What is the best way to go about answering a long answer biology question?

Answering questions in biology that offer more marks is all about key words - usually the examiner has a few of these in front of them that offer a mark simply for using the word in your answer. The good thing for students is that these are often the same in similar questions, so you can learn to look for questions on particular topics and include those key words you've learnt for that topic. For example, a 4 mark question on gene modification if probably looking for the key words 'enzymes', 'splicing' and 'replication'.