You should be able to tighten the post clamp with an allen wrench (or if it's a quick-release, by spinning the handle, sorta). The derailleur can easily be adjusted, too.

I've found this site really useful for quick guides on misc maintenance: http://www.utahmountainbiking.com/fix/

I have a cycling map for Boston, and assuming that the Denver one is at all similar, you'll probably find it very helpful for figuring out good routes around your area.