LOTS of Boyz! Max out your troops choices and make sure there are alot of Big Shootas in there, I use 3 in each squad.
Don't waste $ and points on bikes.
Get a few trucks, one for the boss for sure.
Even though they get a bad rap I like Stormboyz, they excel at stopping those pesky Havoc/Devistator squads from picking you apart from long range.
Power Claws for everyone that can take them (nobz etc).
I play the footslogger style, just flood across the board. You lose at least one squad on the way but the more dice you roll the more saves your oponent has to roll.
Basically, if they shoot at the boyz, the trucks and Stormies are going to be chewing on their asses soon, if they shoot at the trucks or try to get the Stormies, the mass of Boyz will be again, chewing on their ass.
Orks are awesome fun, the basic rule of thumb is to keep rolling as many dice as possible and screen the really powerful stuff.
JHC