This site answers some of the basic questions,
http://www.realtraps.com/faq.htm
There are several options, but the first thing to do is, find out what needs to be treated. Here too there are a couple options. Easy (non techy, but time consuming) Moderate (computer savvy, but super efficient) and Hard (you are not a true AH if you dont do this
).
Easy: Get a RS Sound Meter and make the test tones CD from here
http://www.realtraps.com/test-cd.htm The site also gives you the basics on how to measure the room response. Once you have a FR plot like this, you will know where the peaks and dips are and can start troubleshooting on what room issue is the most likely suspect.
Once you have the FR, start playing around with things like, speaker placement, toe-in, sweet spot location, etc. in conjunction with AVR built in room correction to get the best you can.
Moderate: Download a software like Room Eq Wizard to help you get the FR plot. It generates the tones and plots the graph and much much more. Now add room treatments to the Easy option and optimize.
Hard: Use Moderate approach but add a dedicated piece of equipment to do audio processing in addition to adding room treatments. Eg. Behringer DCX2496 or BFD 1124P. The software mentioned in the moderate solution lets you determine and up parameteric eq correction and you can apply them in the aforementioned devices and obtain the best possible room response.