The following is a procedure I have used with success many times. Maybe it will work for you:
The fun part
1. Find the best location possible for the speakers - for the mains this is fairly straight forward. for the surround and sub(s) you may want to test them a bit.
The Really fun part
2 Treat the environment directly surrounding the speaker (behind and below usually) with sound absorption / isolation.
The really really fun part
3. Add processing to the speakers (EQ normally. Sometimes the automated EQs work, but ALWAYS test against your ear with familiar music or program material. In the end, always go back to your ears). You want processing to be in the signal chain during the speaker leveling. If you level the speakers dry and there is a significant curve, you may defeat all your hard work once you are playing back music or a movie through the processing.
The exciting part
4. Level the speakers:
Play band-pass limited pink noise through the system. I have found one octave (500-1k or something like that) works well for music and two octaves (500-2K) for movies. (if you don't know what you have, that is not going to be a big deal. In a crunch I have also tuned systems with full range pink noise, but this is not ideal). Start with playing the band-passed pink noise through the FL, FR, C speakers one at a time. Position the SPL meter at the listening location and at the height of the ear. If you are using a directional SPL meter I have found pointing the meter directly at the speaker you are testing works well. If you are using an omni mic you can just have it point to the screen during the entire test. Ideally you would mount it on a tripod. The Dolby Digital and DTS theater spec is 85 dB SPLC for each of the front speakers (this assumes the pink noise is playing at -18dB FS - this will provide an individual speaker peak of 103 dB SPLC at 0dB FS). This maybe really loud for normal listening - be careful not to blow your speakers either (you could start at 75 or 80 dB and work your way up or down to a comfortable listening level or your normal listening level.)
Surrounds are to be levelled at 82 dB SPLC (again through band pass limited pink noise), but I tend to goose them up a bit to 85 (that's just my preference).
The sub is a bit trickier. You HAVE TO band-pass limit this pink noise signal - most likely the disc already is and so is any tone generated by the processor.The tricky part is this: There is a 10 dB gain boost as part of the ".1" channel in a dolby or DTS environment (Sony's and Meyers's may also have this, but I have never set up either of them) - this means that you tune your sub to 95 dBC instead of 85 dBC IF THERE IS NOT PROCESSING. Most consumer and home theater processors do this automatically, so I would start with the 85 dB SPLC level and work your way up if you want more.
The Successful part
Once this is all done, play excerpts of lots of different material with which you are familiar. You may find yourself thinking the sub is too loud or something like "the left surround speaker is not loud enough" - trust your ears. If it does not sound like how you want it, adjust it - you can always retune the system.
I'll see if I can scrounge up the Dolby and DTS specs as a reference.