Check out Ethan Winer at http://www.ethanwiner.com/acoustics.html

I had a studio in a square room where you could hardly hear yourself speak for reflections, music was a pain, all bass rumble. I made up three bass traps with Rockwool heavy duty mineral wool insulation in wooden frames and stood them in the corners. It was a difference like night and day!! I didn't bother with the forth corner.
The frames were 12cm thick with two 6cm layers of insulation held in by chicken wire. I covered one side with cloth for looks and put little roller wheels under them so that I could move them around easy. The insulation is fireproof too. Check google for bass traps, there are loads of ideas out there. I saw one instance where one person just rolled the insulation into columns and stood them in the room. They just seem to suck up all the excess bass. For the reflection problem, any uneven surface helps, book shelves, furniture whatever.

Chris