Be aware that in addition to reading and learning on how to use a compressor, many great settings will sound invisable. In other words, you won't necessarily hear the compressor as it is working. Think of it as an automatic volume control rather than a sound enhancer. In first learning how to use it, you may want to put it at extreme settings so you can hear what is happening.
Then back off on the adjustments to a more reasonable setting to compress more in line what you might actually need to acomplish. If a track sounds great because it only had some mild form of compression on it, chances are the track was probably good to begin with. Generally with the lower cost units such as your 3630, the greater settings are where the unit starts to show its limitations, not to mention the general overall coloring of the sound, even in a bypass mode. Read up as suggested and I think you'll gain a lot just knowing what the unit is supposed to do, rather than just trying to hear it working. Sometimes even the best of ears cannot hear a well set, high end compressor in use and tell if the track was that way on the onset, or had compression added in the chain somewhere.
