If it squeaks when you just push down on the saddle, check pivots, saddle, or shock. That doesn't sound like what is wrong with yours, so......
Take the chain off and see if the cranks spin free and and easy. If it is grinding or rough, check bottom bracket. Otherwise....
Sit on your bike, squeeze both brakes so you don't move, then press on the cranks to test for on-power creaks. Basically you apply enough force to your cranks to cause a creak, and have a friend listen/feel for where the creak is coming from. Could be pedals, swingarm, derailleur hanger, or dropouts. Just have a friend help locate the sound because it is impossible for you to locate it while standing/sitting on the bike.
If I had to guess, I'd say check your derailleur hanger because that's usually where my creaking comes from on my Heckler. After I grease it, no more creaking.