There are three key ingredients to a good 30 mark question: A strong arguement, explanation of key concepts and then revelant, and as recent, examples as possible.
Although you have a short amount of time in the exam (about 35 minutes to answer a 30 mark) first take time a couple of minutes to decide your points which will help you maintain an arguement throughout. Lets look at a question together:
‘Gridlock is an inevitable consequence of the US system of government.’ Discuss.
I have underlined key words of the question which is a great way to keep focused to the question. The question wants you to focus on the concept of Gridlock and that it is 'inevitable consequence'. Now to start thinking about points. A great way to structure 30 mark essays to show you have acknowledged the whole arguement is to follow a simple:
Introduction, Agree with statement, disagree with statement, problematise/alternative, conclude.
Introduction: Keep it short. Explain the key concept within the question- What is Gridlock and why does it happen.
Agree: How is it an 'inevitable consequence'? Explain the realted concepts that causes it to be 'inevitable' and incluse your key terms eg. Through the separation of powers that is entrenched in the consitution through the set up of a bicameral legislature allows Gridlock to happen between Congress and Senate. Make sure you explain these concepts and then give relevant recent examples where gridlock has happened because of this. You can then comment on how this was a 'consequence' and how it hindered effective government as a mini conclusion to your point.
Disagree: Here you can acknowledge the counter arguement. How is it not 'inevitable'? Eg when Congress, Senate and the Executive branch are all controlled by one party. Examples of Bi-partisanship and growing centre politics. Say how this directly how strongly this disputes your agree point in a mini conclusion within your point.
Problematise: If you have time this is a great thing to do and shows you are engaging with the question. See if you can find an alternative point to make or 'problematise' the question. For example here you could agree with the 'inevitability' of Gridlock but then disagree that it should be classed as a 'consequence'. You can refer back to the Founding Fathers and suggest how they would have wanted Gridlock as a sign to show the checks and balances through the separation of powers. Or you can comment how some perspectives would see it as a consequence eg from a reformist view it would hinder progressive changes whereas from a constitutionalist would see Gridlock as a sign of the consitution still working.
Conclusion: Find where your arguement lies strongest. State it as your answer and why it is more convincing then the other points you have explored.
So there's a basic way to approach a 30 mark question to make sure you get the key ingredients in. Remeber although there isn't much time there is always worth in reading the question carefully, underlining key words and making a short plan!