It would also depend on how daring you want to photo to appear. Finding a building that no one is using and including it in the picture adds a little different element to the picture. Even if you show the empty parking lot, the building seems to add something to it. Pictures in some trusty woods are nice, as are ones taken in a meadow. But, add something that is usually seen as being public, or man made, and it is totally different. Train tracks are a good place (but try to find some that aren't used any more so you don't get a train running you over), as is under or beside a bridge (not on the road and still secluded from sight from cars passing by).Be careful when choosing your area. You don't want to get arrested. Most of all, be creative. I agree about overcast days and the lighting issue. That is why woods are good. They offer shade. Other places, if the light is right, can add a lot to the picture too. Use your imagination! All of my pictures were taken with a tripod and the automatic timer on my camera. You can get some great photos that way.
Good suggestions. I like the view from above. So get the camera as high as you can. Trees can be used for support but you will need some method to support your camera (assuming you don't have a tripod). Rig up some type of strap to support it. You can use some creativity for this. Digital cameras are free to develop so take plenty of pics. Also, have fun!