Which distribution should choose to start?
I think that Mint is the best bet for new users. Having said that, I would also like to mention Mepis, which has a very friendly and helpful community. Downloading a liveCD of either of these distros would give you a chance to experience Linux and decide if you like what you see. Just note that a LiveCD runs a bit slower than a normally installed distro, but it's good for testing purposes.
Check out the "distro choosers" (several to choose from) to help you decide which distro is right for you. Before jumping into a Linux distro, you'll want to check out the hardware compatibility page on that distro's web site. It could save you alot of frustration.
Just Google "Linux distro chooser" and you'll see a half dozen at least. They're basically just questionnaires that use your answers to narrow down the choices for you.