Start by doing market research. Look up what video editing companies ask. Check those scriplance.com and elance.com type of sites for example to get an idea. There are probably sites more specialized on design/video editing too.

Anyway.. after you have got decent amount of prices you can take an average to see how much your skills are worth. Since you are beginner you should obviously ask much less at first of course.

You should definitely make some sort of web site for your services too.

Good luck