YEAH this is such a good thread!
I agree with everything that's been said so far... just to add/reiterate (oh how I love to repeat things)
-yes, skate low! Derby stance, all the time! When you are in derby stance, your stride should get *bigger* - did you every try that thing where you lean against the wall, standing up straight and kick your leg out diagonally out/back as if skating, then again while getting really low? If not, try this. Go and do it now! It shows you the difference between skating low and skating upright. Bigger strides = more ground covered = faster!
-having said that, I tend to hop round the track like a frightened bunny quite a lot of the time - just saying this to demonstrate the fact that everyone has a different skating style, and it might not be best to attempt a dramatic change in how you skate for the first time during an assessment so work on your skating stance, strides etc. one step at a time. Any time you are on track is an opportunity to work on this - warm up skating included.
-skating the diamond is the dog's baws. Right out in the middle of the straight way and right in on the corners. If someone is in your way, hop around them - don't give yourself a load of extra track to skate just because you don't want to get too close. You can even say 'excuse me' if someone is in your way and going slower than you - they might move a bit and let you zoom past!
-crossovers, crossovers, crossovers! People have different preferences about how and when to do these, but good crossovers will speed you up no end! If you can get a bit of bounce into your crossover, you'll be able to basically run round the track using these. You don't want to just 'step' one foot over the other, you should be pushing hard with the leg that isn't doing the crossing (if that makes sense) and leaping rather than stepping. If I need a burst of speed, I use these 'running crossovers' almost all the way round the track. But this isn't really sustainable for 5 minutes (it's really tiring!), so you mostly just want to cross over on the corners but make sure they are powerful, hoppy ones.
Capiche? I feel like this might have made less sense outside of my head...