Most bike mechanics will tell you that a creaky bottom bracket may be easily corrected with a tune-up and inspection. This is because the issue often originates from parts other than the bottom bracket.
Items such as chainring bolts, pedals, and crank bolts can easily be torqued back to specification and solve the issue. The bike seat and seat post can also cause this issue. If the noise persists, it may be time to maintenance your bottom bracket. Normal greasing and a tune-up will ensure the part works into the future. You can also find guides online or through your local bicycle repair shop, as the bracket is a standard bicycle part. Here is an excellent guide created by our friends at Park Tool.