This tutorial by Shachar Gilad of Waves will guide you through the basics of mixing vocals:

• Reducing harsh “S” sounds (sibilance) using Waves DeEsser plugin.
• Using Waves Renaissance Equalizer to roll-off low frequencies that add unnecessary noise to the mix, and to brighten up the vocals in order to cut through better.
• Using Renaissance Compressor to even out vocal levels throughout a song and make sure every word is heard well.
• Adding depth to vocals with TrueVerb.
• Adding space and locking the vocals to the tempo of the song using the SuperTap delay.