This isn't a SSFG thing. You'd probably get a better answer here.

That being said, it can be:
- Pedal spindles
- Pedal bearings
- Dry chain
- Chainring bolts
- Crank arms
- Bottom Bracket shells
- Bottom Bracket bearings (if it's loose ball)

The bottom bracket is the most time consuming. I'd lube and or tighten in this order (and check for the creak after each step):
- Lube chain
- Grease and tighten chainring bolts
- Grease and tighten pedals
- Grease and tighten crank arms
- Service the bottom bracket


Trust me. I had a creak last week. After removing the rear wheel, pedals, crank arms, BB shells, BB ball bearings, cleaning and lubing the ball bearings and reinstalling ALL of that. I found that the creak was coming from the master link on my chain. ONE drop of lube would have saved all of that work. Seriously...one drop.