Depends on the mic, depends on the sound you're trying to get, depends on the quality of the compressor, depends on the compression settings, depends on the voice of the person you're trying to record, and I think you get the point.
Tips to get a good recording: GOOD cables, GOOD mics, GOOD pre-amps, GOOD recording environment (meaning booth, room, etc), GOOD audio recording device. Don't record with effects (can't believe people actually do this). Don't allow any clipping, and don't be scared to use compression.
Your questions are very general and so are the answers to them. To get GOOD answers, you've got to tweak things according to your environment & setup.