Apologies if this has been answered elsewhere, but I couldn't find a direct topic related to my question.

I've got a project that's been shot on Canon AVCHD at 24 fps - edited in FC Express. The project looks awesome in FC and when exported at highest rez .mov format - but starts to tear (looks like de-interlaced video?) and ghost (trailing images especially where there's extreme motion in the shot) when I shoot for final files below the 500mb range. I'm a bit of a noob with digital post, especially where compression comes in, and this is likely my operator error - but in the end, I need a final size that's uploadable and I want it to look as good as possible. Is this happening because it's shot in 24fps and video is in 30?

How do you more accomplished folks export your files for max quality and file weight? Any help you can give would be greatly appreciated. Thank you!

I think the ghosting has something to do with the frame rate, either your export is set to a different frame rate, or there is something wrong with the project. I don't use that frame rate though so I don't know.
So you are exporting this video for the web/computer playback (as opposed to dvd)? If so, I would export quicktime (or possibly mp4) as h264, with "best" settings.
Video tearing is usually inconsistent and comes from playing back, and not burned into your video. So you need to find a file type that does not tear.