When it comes to Eminem's rhyming technique, a lot of people claim Eminem alters the pronunciation of words in songs to make them sound more like rhymes, but until his post-2002 songs, that was VERY rarely the case.
Eminem hardly ever changed the pronunciation of a word from how he normally would pronounce it in the actual delivery. Examples of him NOT doing it:
What's this bitch retarded/Give me back my 16 dollars
If I could swallow a bottle of Tylenol I would/And end it for good, just say goodbye to Hollywood
Or stole my seat in the lunch room and drank my chocolate milk/Every time you tipped my tray and it dropped and spilt
Please don't let me be pigeon-holed in no regular job/Yo, I hope you can hear me homie, wherever you are/Yo I'm tellin you dog, I'm bailin this trailer tomorrow
In Eminem's head when he's writing the lines, he's hearing certain syllables pronounced differently in a different dialect (bitch re-taw-ded/16 daw-luhs), (Tylenol I would/bye to Hawl-y-wood), (chah-clate milk/dropped and spilt), (regula jawb/eva ya aw/tellin ya dawg/treh-la tom-aw), but in the actual song, he's using his own dialect and focusing on the "voice acting" part.
And that's one of the things that made him interesting to listen to, as opposed to listening to lots of rhymes with words that sound empty because the rapper is just thinking about enunciating his intended rhymes as opposed to saying what he wrote like he means it.
The astute rap fan/listener will notice the rhymes Eminem wrote anyway.
A lot of rappers (especially of the underground variety) could learn a lot from prime Eminem in this aspect.