There's lots of ways to do it, and there's tons of info in [ame="http://www.amazon.com/gp/product/0155062425?ie=UTF8&tag=backmask-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=0155062425"]Aldwell and Schacter's Harmony and Voice Leading[/ame] (which was the required theory text when I went to University of California):
If you can find this book used at a good price, go for it. I sold all of the books I used in college EXCEPT for this one - it's an awesome reference.
Specifically, one technique that is great and can never really become cliche', since it's very specific to each piece of music, is common-tone modulation - where one instrument (say a guitar) holds out a note while every other instrument rests, and this note is a common tone to both the old and new key. Then, enter the new key around the held out note. Blue Oyster Cult's "Don't Fear The Reaper" is a great example of the technique (at the end of the midsection, going back into the verse.)
One strategy I employed while I was a music major was to find examples in my CD collection of techniques discussed in the book. Pretty much everything in Aldwell and Schacter happens at some point somewhere in metal, because modern metal is more similar to classical music than it is to blues at this point. If you go the Jazz/Pop route with theory, rather than classical theory, you'll find that it's a lot less relateable to most metal.