main characteristics of constitutional convention in westminster
Many rules are followed by political institutions in countries using the Westminster system of government that are neither codified in legislation or formalised by judicial decisions. These unwritten laws have been referred to in the past as rules of political morality and the unwritten maxims of the constitution, but have since eventually been solidified into the generally acknowledged term of a constitutional convention primarily due to the influence of British legal scholar Albert Venn Dicey. 
There are different views on what form a constitutional convention takes, one being that of a descriptive statement based on what actually happens, and two that it is a prescriptive statement on what should happen based on ethical and constitutional principals. In a way neither is incorrect, like the first view some conventions exist and are followed merely because they are the widely accepted routine business practice and like the second view others have and are formed based on ethical and constitutional principals. 
Some well established and widely known conventions may have developed to avoid the formality of a change of law, the development of these practices allows for legislation on that particular aspect to be avoided, essentially saving the time, money and publicity that would otherwise go into making or changing legislation. 
The development of conventions is one of growth rather than planning. For example, whilst originally and still at law, section 2 of the constitution provides that the governor-general is appointed by the Queen, today in practice the governor-general is chosen by the current Prime Minister, the Queen attempting to choose the governor-general in Australia today would most likely be considered to be objectionable to good constitutional practice, whilst if this was attempted closer to the time this convention was first adopted, it would most likely not have been considered so . 
It is not uncommon for a convention and law to intersect, the convention of the prime-minister selecting the governor general clearly covers the same subject matter as the law for the Queen to be able to select the governor general, as is the case in the examples circumstances, one may be thought to be more important and nullify the other. 
Other more minor conventions are formed from the day to day workings of the government institutions, which have formed from social expectations and the usual accepted business dealings of the day.
Enforcement via Public Opinion
Disputes may arise from conventions as to their existence and/or content and are enforceable in differing ways. Often disputes outcomes depend on the public opinion. Conventions regulate the conduct of those holding public office, people wishing to hold such roles much observe the restraints which are imposed upon them.  When a politician or a judge acts in a way that is considered out of line with the preconceived notions of their office or stature, even if it doesn't breach an actual law, usually professional peers, opposition or public opinion demand them to relieve themselves of their position. Positions with roles which have now become more limited, such as the aforementioned instance of the Queen and for instance the diminished power of the governor general in relation to the executive powers now conventionally run by the prime minister and cabinet, know that to overstep these conventions, even though the law states differently, would no doubt bring about whatever smaller power they still hang onto being abolished all together. It is also true that conventions are not laws and minor ones may and most likely are, broken or ignored all the time without penalty. 
But conventions are not only followed because of the negative implications that would befall those who did not do them justice, they also express a constitutional value that should be strived for, with then being described as a positive political morality  , not just something to be adhered due to threat of punishment.
Enforcement via Law of the Land
Dicey argues that whilst public opinion is one way that these conventions are enforced, some conventions are actually secured by the law of the land, giving an example from the United Kingdom at the time, namely the convention of parliament assembling once a year. If parliament were to not sit for two years, this would be a breach of the convention but not of any actual law. Any ministry or person connected to the government that tolerated such a breach would come into conflict with the law of the land. The annual army act would expire and attempting to control the army would breach law. Which would also either cause the army to disband, or act on its own to the detriment of any member of the army right down the soldiers, whose actions could easily find them liable in a court of law. Large portions of tax could not be collected without the collectors finding themselves in breach of law and subsequently, what tax was collected would be illegally gained and not legally be able to be spent. Persons acting as middlemen such as officials were not exempt from legal liability and would be suspected to refuse obedience to illegal commands. All this would find the government not only opposed but helpless. This convention, whilst not legally enforceable, nether the less could not be neglected without causing thousands of people to commit illegal acts that would be recognisable at court. 
2. How important is the role conventions play?
Important because they allow the law to evolve, was always intended by the founding fathers when they created the original constitution that these conventions would exist and be able to keep the constitution up to date with the changing times ideology and practices.
Whilst significantly important in Australia, is even more important in the United Kingdom which does not have a formal written constitution. 
Constitutional conventions as mentioned prior, cover a broad and varying range of areas. Whilst some are relatively minor and are broken or not adhered to on a daily basis, others are rather important and in circumstances, circumvent actual legislation or judicial decisions.
Why they exist
Was always the intention of the finding fathers etc. legal online commentary.
Because constitution is based on a system of responsible government. - Legal online notes as well as article.
The constitution or system of government, including the conventions within as much wider concept than the law of the constitution. 
Constitutional Referendums & Conventions
The meetings, not the rules.
Important Australian Examples
The office of the prime minister is not even mentioned in the constution Stuff on thomas and ruter last part.
-Governer general etc.
Mostly fictictious even though more solidified than any other at law.
The Article The governor general as commander in chief talks about the governor general as being a “mistake".
Highest decision making body, yet no power vested by statute.
Shift of power from britian to australia without change in constitution
Australian constitutional crisis of 1975 ?
In 1975 there was what is referred to as a constitutional crisis involving a convention implying that if a position in the senate was vacated, someone of the same party would fill it as the person who had vacated. However, the opposition was able to block supply in the senate with the support of non-labour senators who had been chosen by non labour states to replace labour senators, although this was technically legal, there was a convention that the senate should not do so unless in extraordinary circumstances.  This eventually lead to the dissolution of blahblahblah
Stuff about these conventions failing?
Engineers case? Maybe, convention of state powers? Or is this more a doctrine?
3. Should some conventions be codified?
Views concerning codification
One view is that constitutional law should consist of these conventional rules of conduct governing the exercise of official power which are recognised as obligatory by the three branches of government.  Another is that the constitution should be changed to incorporate these conventions and subsequent laws which are not contained within so that an average citizen would be able to understand it on its own. 
Others believe that just establishing them as something below law, but more than mere practices would be sufficient and some believe that there would be nothing to be gained from codification. Many, however, agree that codification would be an onerous task, not to be taken lightly. 
It is possible that constitutional conventions could be enacted by legislation. However, due to the nature of conventions, being of such a broad character, much time would need to be delegated to working out the specifics of each individual convention, evaluating conflicts that would surely arise and working out necessary future conventions, not to mention that since they cover such a diverse area it would not realistically make sense for them to be put in the same piece of legislation together.  To further complicate matters, whilst some conventions are firm and rather clear, some are relevantly loose and no one really knows where the boundary lies.  Even some well established conventions may be vague in application, with definition open to argument, arguments which are when they currently arise hardly ever definitely resolved.  Sometimes arguments about the existence of conventions are so complex and arguable in nature that they span years, such was the case in 1973 where letters from the Queen, refusing a states petition to the privy council generated a heated debate lasting all the way into the 1980's about preconceived conventions involving what circumstances the Queen is advised by which country or states ministers and the united kingdom's neutrality to the conflict between states and the commonwealth, whilst all these conventions were later deemed unnecessary by the Australia act, now available government information from the United Kingdom shows nearly all these conventions to be false. 
Views as to why codification shouldn't happen
A codified form of conventions would be hard pressed to keep up with the inevitable evolution of socially considered constitutional values, as well as the actual practices of the . If alternatively, conventions were not recognised as conventions any more until acceptance and codification, then the evolution of the system and ability for the government to keep up with current business practices would no doubt be heavily wounded in this regard. Both of these would no doubt hurt the evolution of law within Australia as a whole, making it much harder pressed for politicians and those involved in the constitutional process to keep the law in line with the day, as well as wasting valuable time and tax payer money.
Views as to why codification should happen
Codification would create a more legally bound government and political structure, where what were conventional guidelines would be enforceable at law. This would no doubt act in the public interest of having a more transparent government. Having a constitution of accurate description would allow for the public to more easily judge actions committed by politicians as unconstitutional and political entities would know where the line stands, to further refine and define the rolls based on such.
Whilst currently a lot of constitutional conventions maintain a level of secrecy, one view is that the more information available to the public on such matters, the more easily those in charge of making decisions or commenting on constitutional decisions would be able to come to an agreement on the appropriate action. The secrecy of these conventions can lead to misinterpretation of the current form of the constitution, as was seen in the events prior mentioned in the 1973 state's appeal to the privy council issue. Increased public access to government documents on constitutional conventions at the very least would give more substance to the conventions and enforce the constitutional law system.  Actual codification would no doubt fulfil this same role.
There are views that the current form of the constitution is a mystique of ineffability, something only professionals and those knowledgeable can speak of and that it would be better if the constitution was fixed as to refer to simple statements about what the actual political system is and is supposed to be. As previously discussed, the current constitution still refers that inherent executive and military powers are given to the Queen and the governor general amongst other things and makes no mention of the conventions prevalent to the prime minister, cabinet or the need for a government to maintain a majority of seats in the lower house. What there is of the current practice of government in the words of the constitution that is currently used is obscure and bordered by many obsolete provisions that those not knowledgeable on the area would not understand what to make of it.