depends,
are you grabbing them from TV, VHS, DVD, blue ray, torrents, tube sites ?
most people use free progs like virtual dub, there's also avidemux,
or the ones that came
bundled with their tv card or PC.
then there's pay software , video suites like nero, etc.
visit videohelp.com , a site with lots of info, apps, guides, to get an idea
you can also check doom9