Before you do any work with computer files you should be aware that video
files are often very large. Files downloaded from a digital (DV) video camera, for example, represent
3.56 MB per second of video. This is
equivalent to about 200 MB per minute or 10GB per hour and since you should
allow the same amount of space for the editing process editing an entire one
hour DV video would require 20GB of free space on your hard disk! Note that your computer must be able to import and export DV signals if
you wish to edit DV files - this usually means purchasing a DV editing card such
as those produced by Pinnacle
for a few hundred € or a few hundred USD. Your DV camera must also be able to
both output and input DV signals.
To avoid the space requirements of DV, you can also work with low resolution,
low frame rate videos (frame rate = number of images per second so low frame
rate = jerky video). Many digital 'still' cameras can also make short low
resolution videos that can easily downloaded to your computer, probably in MPEG
format. These can be edited and then incorporated into other programs or emailed
or added to web pages.

Two warnings: I have always found digital video editing to be a frustratingly
unreliable experience - Premiere often crashes, particularly at the moment of
attempting to export the final edited video file. This problem can be minimized
if you save your work very often. The project file associated with each
editing project is actually very small and quick to save - that's because
it's not actually a video file, instead it is a set of instructions that tell
Premiere how to compile the video.
Also, I have found that video files, whatever format they are in, are quite
often 'badly formed' such that they might work in one context but not another.
For example, an AVI file that fails to open in the Windows Media Player might
still open in Premiere. Or a QuickTime movie in an Internet web page might not
be compatible with Premiere once downloaded.