Are they clipping from ahemmed .avi files or ripping DVDs? If the former, this link re: using VirtualDub to clip may be all you need to know (it got me by forever, until I needed source that wasn't readily available as already-ripped .avis for ahemming).

If ripping from DVDs and clipping, talitha78's Vidding Tech for People who Hate Vidding Tech was hugely useful for me to get started. I do a lot of little things differently than she does (I use the xvid codec, for example, which I can explain if it would be useful) but that link at least helped me get started with both DVDDecrypter and VirtualDubMod (both free) for ripping and clipping.