Don’t forget the most obvious thing: be sure your microphone is as close to a unidirectional microphone as possible (at least cardiod — super-cardiod preferred — and most definitely not an omnidirectional mic) and is pointed directly at your mouth with no other major sound sources anywhere near the line-of-sight from your mouth to the mic (for instance, no speakers behind your head). I recommend a high-quality headset or lapel mic.