Walk up any steep hills. It's not worth it going into the red for those relatively short distances. Makes the fixed friendly parts more enjoyable. Audax timings are generous, so take your time.
My bit of advice is eat plenty and often and always keep snacks for when you bonk. When you bonk on a fixie on a 200 it feels like your legs grind to a halt as there is no where to go. Eating will make everything better.
Ahh, I was going to do this but it clashes with a friends wedding. Hope you have fun!