Good lord - just that?
Just a couple of things that spring to mind that are useful;
1. Trim - being able to trim your aircraft helps to reduce the forces on the stick so you don't have to work so hard to fly correctly and a properly trimmed aircraft will be faster and more responsive than a badly trimmed one - it also makes formation flying much easier
2. Engine management - understand especially the relationship between prop pitch and rpm. Know where your gauges are and how to read them
3. Navigation is really a matter of practice, practice, practice. Bear in mind that Fenrir and BluBear live in Kent and so have a significant advantage in terms of Nav, but spend a few hours in CloD and you'll soon get the hang of it. There's a nice map in the Vault to download if you like - http://dangerdogz.com/forums/files/file/766-clod-channel-map/ - It really boils down to practice in the end though.
4. Situational awareness - can't stress how important this is - knowing where your group is in relation to yourself is paramount. Get separated and you're pretty much a sitting duck. Practice by following someone first. Once you've got to grips with that (and it will take time) then start thinking about formation flying (this will take much longer)
Good luck!