Location, Location, Location
There are many factors to include when placing a webcam such as lighting, weather conditions and how accessible is it going to be. If the webcam is facing the sun it could burn the retina if you have an indoor webcam. If you have quite a bit of money to spend I suggest buying a outdoor webcam.
You have to make sure that this webcam will be sturdy against whatever the weathercan throw at it. Most webcams outside have some form of shelter such as a wooden box secured to the ground.
If your prepared to put some time into this webcam to make it a good one, buy a container for it and make everything secure. You want to make the webcam accessible incase anything goes wrong. If it takes some time and effort to get there then you may have a problem.
Onto the location of the webcam.
The webcam needs to have a good wide view where people can see what is going on. It shouldn't show anything boring, you will need to remove anything that has a possibility of getting in the way of the webcam, eg. twigs, branches etc..