True! I'd work inwards: checking the pedals then cranks then BB for tightness, then give the pedals a quick service first, failing all that, then pull off the cranks [check for any cracks] and BB, grease the threads and mating surfaces and re-install.. Creaks are a notorious pain, peculiarly, it may not even be the BB at all, and if all the above [and all the other advice on here] doesn't fix it, check the bars and stem too! Good luck, David.