Test drive as many as you can. As per previous discussion, different designs feel and perform very differently.

Although it seems like a simple thing, let the shop fit it for you. A good fit is key for both efficiency and comfort.

A lot of good bike shops will offer a couple of years of free tune ups with a new bike purchase. Use that time to learn about bike repair and tuning and you will be easily able to take care of it yourself by then. It's actually pretty simple stuff.

With great power comes Awesome irresponsibility.