this has a listing of all the great distros ("packages" of linux) and some info about them
from experience, the first thing to do is to learn about harddrive partitioning, files systems, and what all those mean and do (i learned from the Partition Magic program's tutorial)
another place i learned a lot was from the redhat's website: www.redhat.com;
find some of their documentation and read it, all of it; slackware has a good book too at www.slackware.com
finally, you should learn what all the different parts inside your computer are and who manufactured them (specifically find out about your video card, sound card, and monitor horizontal and vertical sync rates; perhaps find out motherboard manufacture too)
as for what distro to recommend for you depends on you yourself; like someone once said, "if you've always depended on the operating system to do your work, try something like mandrake linux; if you discovered regedit in the very early using of linux and perhaps learned to modify it, then go for slackware or debian"
of course you don't have to be that extreme, but from experience again, starting out with something a bit more challenging like slackware will be a lot more rewarding in the end (mainly in the ability to solve problems by yourself)