I'm totally into collages lately. I have a really cool one on my wall (even if it is still waiting for pictures in the frames). So if you, too, would like to do a collage, here's a good method:
1. measure the wall or area you would like the photo collage to be hung
2. tape the walls dimensions onto your floor. (So that the taped area is the same dimensions as the area you will be hanging your collage).
3. play with different configurations by laying the frames you want to use for your collage on the floor.
4. when you find an arrangement you like, take a picture of it. Take pictures of all your favorites. (If you take it from a side angle, instead of straight on, it will help you visualize it better).
5. go through your pictures to choose your favorite one.