After you upload a video onto youtube, analyze how your voice sounds both with speakers as well as headphones. Try to get a consistent level of audio throughout all your videos (I don't want to blow out my ears going from one audio to the next). Make sure your voice can be heard clearly over any type of music or sounds you have going on in the background (the audiance is supposed to be there to hear you, not the music unless you are a music channel).
I would recommend audacity to play around with all the effects they have available. Equalization could give your voice a treble or bass boost if you need it. Noise reduction can take out all of those background sounds and static.