I would normally be happy to help but I'm up at school.
My biggest things are to make sure to have as little rock surface touching the sand/bottom of the tank as possible, having everything on the bottom angled up as much as possible so you don't get much settlement around the base of the rocks. Also securing the rocks is pretty important and will let you make some wild caverns and stuff. I've never secured my rocks because it's always been inconvenient for me and I'm lazy to boot. Try to use as little rock on the bottom as possible.
Another thing to keep in mind is the structure that you want to make in the tank, i.e. the classic "rock wall," the two islands with a channel in between, the single island, the rock pile, etc. There's a million different things, but have a plan in mind.
The nice thing about a 210 is that it'll give you a fair bit of landscape to work with (I'm unhappy with the amount of room I have to work with in a 120 which is a lot of room as it is).
