Breakdowns
 

How do you play a breakdown?

and

Some things i could put into my practice routine to help with them?

I can't imagine they'd be that hard, especially considering they are a break from blasting. Just listen to some and get the feel. 'Liege Of Inveracity' by Suffocation.

okay, im going to assume you mean a mainstream breakdown like all of those shit metalcore bands that have recently sprung up that all fucking sound the same.
quarter notes on a crash cymbal
bass with whenever your guitarist does his little chugg chugg thing
snare half notes.

lol i know what you are talking about with the metalcore bands. But actually the band that got me really into breakdowns was nevermore.

Usually drummers will follow the guitar picking with their kick drums. Keep time in quarters, not sixteenths. You want to keep time on something loud such as open hi-hat or a crash or china that is at least 18".

just listen to bands with breakdowns and go on from there.

its mostly slowed down cymbal with a kick pattern.
but i suggest you experiment with diff tempos on the cymbal, since the feel changes dr4stically as you speed up or slow down.

write a fast heavy riff and slow it down

This pretty much sums it up.