Microphone

Professional KJ's will likely use a mixing board for all their microphone and audio sweetening needs. However if you just want to use the computer as your mixer and sweetener, you can! (make sure you have a fast computer, the more audio processing your computer does, the slower it goes)

You'll probably want a Griffin iMic, since it has a built-in pre-amp. You get much better sound and less hiss if you use a pre-amp. Otherwise you can just plug the mic into your microphone port. Depending on your microphone, you may need a special adapter.

Some day I plan to have kJams manage your microphone and audio effects, but for now I use Audio Hijack Pro, althogh you could just as easily use Audio Hijack (Lite), I like the extra features of the Pro version.

In Audio Hijack, hijack the microphone port and you should start getting sound from the mic. If you do NOT have a pre-amp on your mic, you will need to add the "V4X Effect -> Double Gain" to amp up the microphone signal a bit, tho you wil get some hiss, which you can then try to minimize with a Graphic EQ effect. At that point some KJ's like to add a reverb or chorus effect, to make the vocals sound a bit more like you're in a large theater.

If you also want to sweeten the audio of the music itself, you can at the same time hijack kJams, and add whatever effects you wish.

Keep in mind that digital audio processing (as opposed to using a mixing board) will always introduce a very slight delay in the audio.