Some things that haven't been mentioned:
1) Always shake your shoes, socks, jacket, etc out before you put them back on in the morning. or shake your blankets/bag before you climb in them to sleep. (spiders,centipedes,snakes, depending on where you are.
2) Try to find a spot before dark. Or carry a flashlight (which you should anyways). It sucks finding out you slept on a pile of shit, used condoms/toilet paper, or dead animal remains.
3) Avoid tall grasses or trees which are known to harbor lots of ticks. (but like any bugs - they are unavoidable for the most part)
4) Unless you're out in the country and don't have to worry about it - Tie your shit up in a way that you can hear someone tryin to sneak off with it or in a way that discourages them from stealin from you.
5) This is common sense but - Avoid sleeping in or near someone else's camp or if it looks like its still being used. Or somewhere that looks heavily trafficked.
6) Depending on where you are, don't sleep with food next to you or in your pack (brave/hungry racoons, bears, ants, etc). Tie it up in a tree and don't have any opened packages or leftovers on you especially.
7) Don't sleep in ditches or in depressions of the land that may flood or collect water if it rains overnight. Or somewhere where it will be soggy ground if it rains.
8) Always be prepared for rain.
9) I like to sleep with either a knife ready right by me, or some kind of weapon to use if anyone fucks with me in the night. It just gives me better sense of security and helps me sleep better but that's just me.
10) Like someone else mentioned be mindful of snags and deadfall from the trees. Especially if it's going to storm or it is windy, avoid sleeping right under trees or under the trajectory of falling rocks/debris.
11) For christ sake man, pack out your trash. Don't leave yer litter. And please please please bury your shit in a hole somewhere out of the way. I hate it when people don't do that, it stinks the place up and attracts flies.
that's all i can think up at the moment. have fun.
"Lets Walk With The Earth, Instead of On Her" ~