Another thing you could do is make sure that your recording volume is rather low (not to where it can't be heard/the mic bass-thing is off), so that you can be loud and it won't affect the recording too much. By that point, you could always just amplify the recording, to where the volume's good (but don't think that de-amplifying it makes it better, because the quality's ruined if you record at too high a volume).
(Though, that's more of a suggestion if you use a loud-ish voice when recording. And, yes. This is kind of an alternative to mugenginga's "quietly record" advice.)
An actual tip I can give, for quality (when it's not a volume issue), is to use Audacity. Not necessarily for recording (since a lot of people here seem to use OREMO), but to clean the recording up.
If you have one of the latest versions, you can use the "High Pass Filter..." under the Effects (beneath the divider line-thing). And if you use "Debug", rather than just the "OK", it gets the proper whatever and makes it sound the best it can (only one time is needed. Any more than that and it just begins making it really quiet.).
(I do this with all of my recordings as well as the ones I receive to mix, so it works. Prior to me using the Effect, my recordings sound extremely muffled, even with my headset, so I really do know that it works and I'm not just copying-and-pasting advice. XD)