When your assistant sends off "master" exports to your client make sure that the client can actually play them so you don't get a call at 5:30pm that the video "won't play". And by that I mean explain to your assistant that FCP will export (Export QuickTime Movie) at the codec (yeah yeah I know) it was originally ingested as.
So, for example, if you've shot or ingested something that's DVCPROHD it's likely the client won't have that if they don't have FCP installed. And no, it's not really the best idea to send them a copy of the codec for legal reasons and because many client's I've worked with won't have that kind of access to their machine since IT people love to lock non-IT people out of everything that's actually useful on their computers so you'll end up wasting time trying to sort that out then discover they don't have Admin access.
So a tip: Export your masters in a codec that the client has that they can use and view. Animation, ProRes, Apple Lossless, etc...stuff that they're likely to have by default.
Also, keep in mind what they'll need if they need to do more than just watch. If it's just an approval copy go with H.264, it's small and looks great. If they're on a Windows Box I'd still go with H.264 (seriously, .wmv? No. .avi is dead, although I do like a good .mkv).
If they need to transcode it (ie...it's been approved) to DVD or something send them an Animation or ProRes so they can do with it as they see fit.