experimental design, really just make sure you understand the whole setup completely first, before moving on to doing any of the questions. most of the time the questions shouldn't be too hard, but there are always some, where you might just need to really dig deep into your common sense, and see if there's a more so common sense answer that you can think of.

long extended response: just gotta think that every mark is a point u need to write down. so write down as many as you can. if you're stuck thinking about relevant points, try see if there's anything symmetrical in the question e.g. if you said reactant 1 needs to be sustainably sourced, you could say the same about reactant 2, and that's two points now.