Rather than reinvent the wheel here, let me point you towards the Vimeo Video School 101:
Join the friendly Vimeo Staff as we cover all the basics of shooting and editing videos you can be proud of. We’ve handcrafted these lessons for beginners of all backgrounds, check it out!
This online resource has a series of incredibly simple, easy-to-follow instructions on the basics of shooting and editing short films for the web. It also includes step-by-step guides on the basics of editing with a PC (with Windows Movie Maker) and the basics of editing with a Mac (with iMovie).