It is very easy to get carried away with compression. To avoid this, I try to make a habit of controlling threshold and ratio as diametrically opposed parameters. If the threshold is low, this will increase the amount of compression applied, this is then countered with easing off the ratio. Of course it also depends a lot on the nature of the sound it's being applied to. A vocal track tends to sound more pleasing (in my opinion) with low threshold and low ratio, where the compression rides the sound pretty much all the time, maintaining some the loudness variations of the vocalist, keeping things musically interesting while giving the voice a much more intimate sound and giving relative dynamic continuity throughout the piece. Although a drum track would tend to have a different combined "sweet spot" of ratio and threshold, the technique remains the same. If you adjust one of the two parameters, it pays to routinely think about about making adjustments to the other.