Well, I'd say that the best way to go about this is to just install one of your distros and go for it. Just play with it - that's how I first began with computers, just playing, seeing what happened when I did this, that, and such and such. IMHO, that's the best way to learn - hands on experience... Yea, you may mess something up but in the long run, you'll learn from your mistakes and such...

Personally, I would recommend to install Red Hat - it seems to be the easiest for someone who has never really messed with Linux before. I have Red Hat 7.2 installed on one of my boxes and I like it alot, but I know that there are others here who will stand by other distros.

Just my thoughts...