Hi there! DukeNukem 2417 here, with the first in what I hope to be a series of posts on how to be a voice actor for M.U.G.E.N (or YouTube, if you so desire).
First off: my guidelines for what settings you should use in Audacity (the editing program I use for my M.U.G.E.N voice work).
16-bit .wav format = M.U.G.E.N .SND files will ONLY accept 16-bit .wav files. No MP3s, no 32-bit .wavs, just 16-bit.
15 decibels sound volume = You can go louder than 15 decibels, but I wouldn't recommend it---a volume over 15 db causes clipping and distortion, which isn't fun for anyone.
Remove silence at the beginning and end of the sound = Leaving in silence can occasionally cause corruption within the .SND file. It's better to cut out any "gaps" before and after a clip.
Acquire noise profile = Use "Noise Reduction" in Audacity's effects menu on a small portion of the clip, but take the following suggestion into consideration first...
Run noise reduction (white noise or background noise, not dialogue) = ONLY get a noise profile from a part of a voice clip with white noise or background noise, NOT your own voice.
One more thing: I highly suggest you record your voice over work in a room that's not next to a window, or near any area with high vehicle traffic. Sounds a bit stupid, I know---but take it from me: the last thing you want is to start recording dialogue for a character, only to have some rando blasting country music from a block away and the sound getting picked up on your microphone. Stuff like a light rain outside can be minimized with the aforementioned noise reduction, but I personally wait until after the rain (heh, Nelson reference) to record.
Okay, that's it for the first lesson---tune in next time for some tips on how to voice your favorite characters more effectively!