Interesting guide at the top, cheers.. tho Im gonna go ahead and disagree with the notion of dialing in these parameter values and expecting magic. The best advice I've had is to use your ears and listen as you tweak, rather than worry about what values you set. You will get a much deeper understanding of using your tools with this philosophy, and much better results.
I do have a few guide lines I go by which work very well I'v found. Would be curious to hear others opinions on them. (Btw these guides I use are mostly tested and tried on synthesizers and sample drums, not so much acoustic instruments)
But first, the compressor I use is Ableton Live's native compressor, waves L4 multiband, and Voxengo Elephant limiter.
To start, I always set an arbitrary ratio first. Somewhere between 2 - 3:1, unless its bass, then more like 3 - 5:1
Find the sweet spot with the threshold by gradually dropping it down into the signal. I picture this like a magnifying glass, where you zoom in on the signal and select the part you want to stand out. A shallow threshold will have a rather thin sound. A threshold too deep in the signal and you will start loosing some detail, and it will sound more muddy and not so crisp. Find the point between these two and you will get a sound thats full and big and full of detail.
With attack and release I use similar principles. The more low frequency content in the signal, the longer attack you need. Think of it as weight. The heavier the signal, the more time it needs to move. As a reference, I use around 45 - 50ms for the heaviest bass sounds.
Higher ratio's also need longer attacks too for similar reasons.
Sounds with slow articulation (like pads) can have slow attacks, and with a bit of knee. I find with these sounds the attack isn't so critical.
With sounds that have fast articulation, you need to get the attack right. But it depends what your trying to achieve. If you want to add punch, use a longer attack. Maybe a slightly deeper threshold too, but be careful and listen as you adjust. If you are trying to fatten the sound without increasing the percussive punch, then a slightly smaller attack is good, and maybe a slightly higher threshold.
It also depends on the how fast the transients are in the signal. If you have a fast rapid sound like a quick hihat then you'l need to be careful not to have to longa attack and release. The compressor needs time to move with each new transient.
What I listen to when I adjust attack.. If the attack is too short then it sounds a bit restricted, like its holding its breath. Then as you increase it, its like it just relaxes and exhales, and sounds more open. If you go beyond this sweet spot then it gets a bit flabby and somewhat less responsive (Very subtle changes in sound these are btw..).
Release time is under very similar principles as the attack. Usually just a bit loner though. Ie. bassier sounds need more time to move so a longer release is good (Between 75 - 100ms I find works best with bass). But I find attack is alot more critical than release.
Once I'v set attack and release, only now Ill go back and revisit ratio. Try giving it a little more and see if it sounds better and fuller, or if it sounds more crushed. This will tell you which direction you need to take the ratio in. Find the sweet spot between these two extreme's.
Once you've set all these, set the output gain so the level is the same with or without compression. This lets you AB your work accurately. If you don't do this, the louder signal will most always sound better, but it won't be the truth.
Once you've done this, go back over your settings again, change them all in small increments and find the best spot you can. Keep ABing and tweaking til you have the most optimal settings for all parameters and it'l be mint as.
I find this works very well for me anyway, but these are just a general set of guidelines and may not work in all situations. If ever unsure, just listen with your ears
Sorry to blab on..