I think the most important thing you can do if you're not quite sure is write down ANYTHING relevant you can fit in the space, and drop in as many key terms as possible. Hopefully that way you can pick up at least some marks.(Original post by Libby18)
Erm I'm not sure how to explain, btu when you see a question what process do you go through i.e sometimes im not sure what to write/what they are asking for -I usually can work out what topic or what it relates to.
When practising, I find memorising the mark schemes for longer questions really helps as it helps me get a feel for what sort of phrasing they use when they want you to discuss a particular point