The playhead in the events window will show you the time at which the clip was taken, if you play both and note a point at which the two are in sync (a clapper board is ideal, but you can do something else like drop a book on a table), then work out the time difference between the two clips since the timecode on each camera is unlikely to be in sync, you then have reference points.
The playhead in the project window denotes elapsed time, so by referencing this to the event timecodes you can insert what you want when you want.
For example: You take two shots of the same scene. Analyse the clips and note that Johnny picks up a cup which can clearly be seen in both clips. You note the time this occurred in both clips, lets say 10.00.03.00 in clip A and 10.00.04.00 in clip B, you now know the two clips are 1.00 secs adrift in terms of timecode.
Clip A is your base video and it started at 10.00.00.00, Clip B starts at 10.00.01.00, which is a second later but since the time codes are a second out the sync is now 2 secs out relatively speaking.
You then find a point in the project at which you want to do a cut away, drop a comment marker, let's say it's at 5.00 seconds elapsed time which we know is 10.00.05.00 on the original time code, we can then relate this to 10.00.07.00 on clip B. We can then select the part of the clip we want and drop it onto clip A, zooming in the timescale will allow us to adjust this more accurately afterwards. You then detach the audio and delete it.
If you have your timing wrong (as I may have in this example), it will be noticeable and a little trial and error might be needed. Once you have your time difference for one cut away you can use them for others.
Of course your times are unlikely to be as round as the examples which make it all a little more difficult and you may want to base your cut out points from clip B instead of clip A which needs a slightly different procedure.
Personally I'd get Final Cut, which is what I did, but it can be done in iMovie.
