first thing to do is set your RT settings to "unlimited"
you'll get pretty clunky playback of off-format material,
but it will play.
you can still work the shots in the viewer, of course.
so you can set in/outs there no worries.
but once you cut it into the timeline it gets clunky.
so render as you go might be a good workflow
what settings you chose to edit in depends on what footage you have most of.
(and delivery requirement, but you don't have any).
of course so-called B-Roll can actually wind up being the body of your show.
you'll have to think that one out depending on the nature of your piece.
everything will look better in the end if you shoot the same frame rates.
if you shoot the same frame rates, you can pretty much get by without having to recompress the off-format material,
of course FCP6 has beefed up the RT for off-format shots so you can now work with mixed formats.
one big problem still: mixed frame rates are not handled well.
just a simple dropping or deletion of the frames to adjust.
another problem. FCP6 does a simple re-scale of the material to fit the sequence frame-size.
ok sometimes, but when you're cutting 480 shots into a 486 timeline, it's would be a lot better to just place them centrally with no scaling.
(listen to me talking like i know abut this NTSC stuff!.. i read this on another list!)
cheers,
nick