structure is whatever it takes to get your point across, how fast you can write, what examples you have available etc. 3-4 paragraphs seems sufficient.
correlation and causation are fundamentals of argument and essays by extension. if an event seems to happen whenever another event does, they have a correlation, but event 1 does not necessarily cause event 2 just based on the fact they seem to come together. there might be an unknown event 3 that causes both of them. understanding how the system works generally is a better approach in my view to memorising essays hoping to get the right question. if you learned in class that the icc has been relatively unsuccessful to date because of its elective jurisdiction, then you can form an argument around the facts, for e.g. that international crime is prevalent, it is not prosecuted as it is fruitless where a state will not cooperate, and suggest that the international system is ineffective in addressing international crime given it depends upon a domestic legal system's recognition of such crime and willingness to enforce it, and you might suggest that the only real mechanism for international enforcement is the coercive powers of the UN, which a majority of states are members of, and that if the security council were more active in utilising their wide powers, it could be a means to force better compliance with international norms. there are then counter arguments that the security council is essentially deadlocked due to the veto power, e.g. russia ukraine and russia having veto power, and that international law is a lowest common denominator game, where due to cultural differences, settling on a definition of international crime can be difficult as certain acts are more egregious to certain nation states than others.
recommendations on amendments is using common sense to figure out why the law is in the current state that it is, and what realistically might solve the problem. it is often the element that pushes an essay into the full mark range and demonstrates critical engagement. oftentimes the answer is that the current system is the lesser of many evils, and the best compromise that can be found with regard to all the other values in tension. if international crime is rampant because of a lack of enforcement ability, it might be suggested that further extradition treaties be entered into or proposed to allow for pseudo prosecution of international offences at a domestic level, or at least a particular type of crime that states are likely to have a consensus that it is in their interests to extradite, as they would want to deal with the offence in their courts had it occurred against one of their citizens.
from a mindset perspective, a fundamental understanding of the law allows you to at least compose a comprehensible answer to any question, even if you don't have a bunch of specific statistics and media articles prepared. there are often high profile and interesting examples you encounter in class that are relevant to a variety of topics and can be recycled or used by way of analogy even in seemingly unrelated topics. e.g. the lindt cafe siege case and its subsequent impact on bail laws, or the kieran loveridge one punch case leading to the lockout laws and mandatory sentencing, which can be used as examples across almost any question on crime if argued right.