Room Treatments - How?

If you desire a "cradle to grave" read on acoustics, the Master Handbook of Acoustics by F. Alton Everest might be a must read.
Minimal treatment usually involves treating your first reflections from the side walls, the wall behind your listening position and the corners of the space.
Room analysis software can be a double edged sword, way to much information to sort out what really matters along with a learning curve.
An inexpensive SPL meter and test tones can go a long way to optimize your bass response.
You should try to have the best bass response possible without treatments before you begin. (based on my personal experience)
My take goes like this on treatments;
1st - first reflections first (very predictable with a mirror and relatively easy to treat)
2nd - the wall behind your listening position (very easy to treat)
3rd - the room corners (this area is where prior analysis helps if you have to tame bass peaks/nulls and can become rather involved to achieve a desired result)
4th - more bass traps along the walls if your corner treatments did not achieve the results you needed.
The reverberation time (RT60) of the space also comes into play as you treat the room.
Its very easy to kill RT60 and deaden the space.
It can be very challenging to maintain/obtain the correct balance of absorption and diffusion while treating a room to keep RT60 acceptable.
Send your room info out to the professionals that offer free analysis.
Keep an open mind and remember that what models well on paper just might not be the final solution for your room and listening tastes.
Costs can be quite minimal if you are a DIYer and the results will redefine your listening experience.

I'll second the consulting with a pro or two prior to throwing in a lot of money towards treating the room.

Ensuring all is set up well and the bass is as good as you can do first, is way important too.

There's tons of DIY info on rolling your own treatments here in the archives if you peruse them. ONline elsewhere too.

it'll sure pay you to do some research here, but it'll wind up being as has been offered so far... it's not an exact science.... you'll have to simply try adding this and that, and then perhaps repositioning things a bit as well.

But do heed the pro's input, and go from there.

it's almost like putting together an audio system... not too much of this or too much of that... it's a blend of items.

Albert Von S once told me to initially shoot for a 50/50 mix of absorption and difusion.

Good luck!

I tried to take room measurements and treat my room, but without experience in acoustics the measurements didn't mean much, even after reading Alton Everest's book and visiting many websites. I finally talked with Rives (they designed a plan that I used), RPG and RealTraps. Then I went through two stages of adding room treatments. The first stage got the room to where Blues, Jazz and Rock sounded good. In the second phase I added more bass absorption along the front wall-ceiling and back wall-ceiling and diffusion on the ceiling. Now I enjoy listening to classical music in addition to the other music. The change is amazing.

After I added the room treatments in the first phase, I had my room professionally measured by an engineer using acoustical software. The engineer created a virtual room, added the treatments and got the hypothetical reverb times. Then we measured the room to validate the calculated results. The software was spot on! It also showed that I need to move my CD rack to get better balanced imaging. In a couple of weeks I'm going to have my room re-measured using waterfall plots to see the final results.