I see a lot of people who are saying they learnt by doing, which is great! I too learnt a lot of what I know by googling the questions I had and browsing forum posts etc. I also watched a lot of tutorials from Video copilot, Film Riot, and Corridor Digital (Sam and Niko). Of course in order to do this you have to kinda be a competent computer user and know your terminology, good luck trying to google something you don't know the name of
If you're an adobe user I definitely recommend checking out the sources I listed above, but if you're a Vegas user then try looking through Arbiter617's older videos (now called Black Plasma Studios or something) he posted some really good tutorials, I think he has a 1 hour long one that goes through like EVERYTHING in Vegas or something. If you use anything else then that's cool, but I would recommend you look into getting Adobe Creative cloud and learning Premiere Pro, there's just so much more you can do with a non linear editing application, plus it integrates perfectly with after effects.