As much as I like the "Pottery Barn look" of doing all matching frames, I thought it would be more interesting (and less matchy-matchy) to do a variety of different shapes, sizes and colors of frames. Plus, I'm not really into precision and measuring the exact space between frames and getting out the level and all that, so the non-matchy hodge-podge idea appealed to me. So, I've been collecting frames over the last few months. Any time I was in Target or Hobby Lobby or Pottery Barn or Michael's I'd pick up a frame. I finally had about 30 frames to work with.
Step 1: Use plain paper, cut to the exact size and shape of your frame to use as a template. I took all the frames I had and numbered them. Then I made a paper replacement for the frame to hang on the wall and numbered it the same as the frame. I used white paper because our walls are tan, so they showed up well. If you have white walls, consider using a darker shade of paper. Tip: When tracing the frame, flip it over and mark the spot where the nail would go. This will save you a lot of time.
(Sorry again for the crappy quality of the pictures. My camera is still out sick and these are from my cell phone.)
Step 2: Put the paper replacements on the wall, where you think you want them. By using the paper and tape, I could place them where I wanted to get the right look without having to drag frames around or attempt to "visualize" (yeah right). This way I could rearrange again and again and get everything exactly where I wanted them without having to make a million different nail holes if I changed my mind.