I always hate when I get a rap
artist in that only has a stereo .wav file to work with, because as previously mentioned, my vocals are going to be sitting most prominently in the 2k-10k range, and this means I'm going to be potentially cutting out some hi-hat and snare from the beat because they were too cheap to invest in the multi-track beat.
*sigh*
But as previously stated, basically what I do to these tracks is the vocals get a heavy dose of compression (I'll usually be knocking off 7 to 10dB at the loudest point on a lot of rap guys) using my CLA 1176 emulation. If you're using Pro Tools, the BF76 works great too, otherwise, pull up whatever compressor you've got on hand and work it until those vocals are level.
Then I pull out my V-series EQ or Pro-Q (again, any Equalizer will work here), and this may be just the room I work in, but most male rap guys tend to have some weird thing going on in the 500-800Hz range that makes them sound kinda muffled. So I'm almost always pulling out a bit of that, using a HPF to taste, and then boosting some air around 10k. If this causes issues with sibilance, I'll either automate the volume on the esses or use a de-esser.
If it's still hard to get the vocals sitting well, I'll pull some of the 4-8k range out of the beat until the vocals are clear. As previously stated, this affects the WHOLE beat, so snares and cymbals and possibly lead synths can be affected. Work with multi-
tracks when possible.