A deer could bed down just about anywhere but they will bed down in certain places more often than others. The most likely places are anywhere they feel safe and secure enough to let their guard down. Cover that is thick and impasible to anything with 2 legs is their favorite but barring that they will bed down where they can get some advance warning of someone aproaching. I can think of 2 specific spots; one is a cedar swamp in the upper peninsula of michigan. It's filled with fallen timber and thick brush and has lots of small dry hills surrounded by muck. A deer could bed down in one of the dry spots and be unseen from 5 feet away and hear the sloshing of feet through wet swamp if anyone tried aproaching them.
Another spot I can think of is on my property in Illinois. It's a small clearing on top of a hill that is carpeted with high prarie grass and surrounded by fields of corn. Deer will put their back to the wind so they can smell anyone aproaching from that direction and face the field so they can see you aproaching that way. There are always several bowls of crushed grass where deer spend the day. The only way to hunt it is with a drive and when we do we always push out a few deer.