How do you study for the Unit 3 Practical Skills exam?

From my experience with Unit 3 both Biology and Chemistry, I'd recommend you look through the practicals, which you can find notes on them on PMT. Do a lot of past papers and just see what they're asking, I also thing you need the knowledge from unit 1 and 2, so a quick revision would be helpful. By the way I got a A on both those papers, just saying what I did.

Well usually they ask at least one question where they ask to write a detailed procedure to find something, so yes you do need to know the required practicals to some extent. Its usually a 6 marker.

alright, thanks for the help!