How do you pick up the singing with out getting feedback in Rockband and GHWt?

I heard something about using a fan or something that would help. I'm trying to hold the mic to the speaker to get it to hit the notes. But every time I make it loud, I get feedback. Every time I make it quiet, the I don't even hit the notes. I'm trying to get these hard acheivements on World Tour, mainly the one Mike checka.
How do you pick up the singing with out getting feedback in Rockband and GHWt?
hold the thing a little back from your mouth that should help alot and if it doesnt work hum the tunes that always works