Great question!!..
Measurements: We (Lars and I) have always felt our best test equipment was OUR EARS!! We use them first and last whenever we test, adjust, tune (whatever you want to call it) a room. We also use TEF, MLS and SMAART to verify what we hear!!
Test Gear: As I said, we rely on TEF, MLS and SMAART currently as our acoustic test systems. These tools are very helpful when making finicky adjustments to crossovers and monitor systems and allow us to "see" things beyond the resolution we can hear (easily)..
BUT.... we feel that there are many things in a Critical Listening Environment that we can hear, that do not easily show up on the measurements. So... use your EARS first and last. Use test gear to verify and quantify what you're hearing. (ie: is that dip at 150 or 200 Hz??). Playback system response is very subjective and we always have to get a feel for what the client is looking for (pretty easy in a Hippity Hoppity install, but always a mystery elsewhere!!).
In a recording (live) room, we seldom do measurements except for a RT-60 test (each octave decay time) when we want to quantify what the final decay time is in a 'live' room. We use our experience do "design" the room to sound appropriate for it's size and intended use. Most of the mid-sized performance rooms (large booths, small live rooms) we design have a "mid-acoustic" as I call it. They are treated very similarly to control rooms (as opposed to "out of control rooms" which we often are called in to fix!!). We try to make these rooms sound natural when we speak loudly in them. This is a really good test. Does your voice sound natural, and does it maintain this natural sound when you YELL!... Whooping and Aaahing in rooms is one of my wierd personality quirks!
So, use a moderate amount of absoption, some reflective (or diffuse) surfaces that are not parallel to eachother, and start listening.. Setup the drums>> what do they sound like?? If it's too "splashy" add some more adsorption.. you know what I mean?
Hope this helps!