FAQ: How do I Get Started with Video Editing?
Most people's first attempt at editing involves beginner-level software such as Windows Movie Maker or Apple iMovie. There is nothing wrong with this approach, in fact it is arguably a good way to get started. Simple editing applications are less intimidating and easier to learn than professional packages, but still have the same general layout (timeline, project bin, etc). You will find it useful to understand how different editing software works, and this is an easy way to see how different applications work. You will quickly outgrow them though, so have a plan to upgrade.
Start by editing home videos or any random footage. You can even record footage off TV and try to re-edit it. The most simple example is removing commercial breaks.
A crucial concept to understand in editing is the method of laying down the audio first, then adding the vision to fit the sound. Music videos are a good way to practice this. Place a song in your timeline and add video shots, trying to synchronise them with changes in the music. The ultimate goal is not to synchronise all video shots with music beats (that's too artificial), but it is a good way to learn the art of audio/video synching.
Put your videos on YouTube and invite comments. This will be a good chance to see how thick your skin is — you may receive some harsh feedback at first.