record at at least 24 bits/44.1 khz. the higher the sample right the clearer same thing with the bitrate. if u record at 44.1 khz its taking 44,100 samples of audio per second some interfaces let you go up to 192 khz so that would be 192,000 samples per second which would techically make it clearer. so higher bitrate/sample rate would make it clearer regardless because a lot more information is getting captured. just like if u had a digital camera with 2 mega pixels vs. one with 12 mega pixels.
after that your preamp does a big job providing the gain and clarity of the gain to your mic. the stronger the signal the better usually and good ones cost gwap. get you a nice preamp though that will help u out more than anything.
last is your mic u want different mics for different tasks your not usually gonna put a sensitive ass mic on a loud ass source or a sensitive ass singer on a mic meant for loud people u gotta find the right mic. price dont matter like they say half of the time your paying for the brand but i will say neuman makes nice condensers but then again ive gotten good recordings with a $50 dollar MXL mic. industry mics are usually condesers: nueman tlm 103, neuman u87, akg 414 for rap, on tweakheadz they recomend a dynamic shure mic i dunno what its called though (not sm57 or 58) go to
www.tweakheadz.com.
also where you place your mic makes a big difference if u put it in the corner of the room your voice might sound kinda boxed in and nasal because theres not much room (and a lot of rappers like to record in the corner i dunno why). i say try to put it in the center where not too much sound can bounce off or if u gotta put it by the wall put some sound deadener behind it (even clothes will work if u recordin in your closet or somehting) every room sounds different and will make u sound a little different thats why people pay hella to make there room sound good.
also all that wont matter for shit if u dont know how to get your shit mixed/mastered. make sure u recorded with some headroom (no clipping) and get them vocals eq'd compressed, reverb and a little delay, chorus effects for the hook and get the whole song squashed to shit for rap.