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Hmm.
My general mainstream hip-hop knowledge says:
Drum beats are important.
Just make it simple.
Then there are two paths you can take after you get yoru first drum beat.
- Modify it for each song part. Each verse containing similar/the same drum beat, and so an and so forth for each chorus. The Pre-chorus will do exactly what it's supposed to do, and lead straight into the chorus.
- Option number 2 is have one single drum beat through the verses, and then crescendoing into the chorus. Then, modify the drums you're using and keep the drum beat extremely loud comparably to the original beat.

Piano is fun.
It should stay kind of quiet unless it's immediately important to the structure of harmony and melody.

Hmm.
I'm trying to think of other things.

OH YEAH!
If it's fast and poppy, you can produce it just like techno.
Prime example: Down - Jay Sean ft. Lil Wayne

References:

For the wax, use Pete Rock.

For the more electronic, use basically anything The Neptunes ever touched.

Vocals, bass and beat have pride of place, obviously. Vocals should be doubled on punchlines (Beastie Boys are a super obvious example of this). Bass drum always seems low-passed and snares/claps are always snappy and prominent.

Hope this helps in some way.

I need a ******** sub. damn it. I think I have it so far though. the dude gave me consolidated audio files, FINALLY SOMEONE GETS IT RIGHT. The only downside is he gave me a stem of all the drums and percussion. So I had to make some new snares and claps. It's coming together though.

Yeah I personally like to keep the piano a little low in the mix. dude wants it loud though. that's all that matters.

It reminds me of Show Me your Genitals