There are a lot of parameters for mounting your bat house and it's construction. I don't recall all of them so it's best to research bat specific organizations.
I remember there should be water no further than 1500 feet. Since we have ponds, that shouldn't be a problem.
I think it has to be at least 8 feet off the ground and away from predators.
It's color depends on where you live. I'm in northeastern PA and mine had to be black to attract as much heat as possible. So, direct sunlight is needed for most of the day.
There are many cheap models out there that are not good. The inside needs to be roughed up so they can hold on. Some cheap ones nail screening to the inside for that reason. You don't want that type.
Here's one good place to start:
BAT HOUSES
www.batcon.org