Take the mattress and box spring off the bed frame. Using a wrench, detach the nuts and bolts that hold the bed frame together. Remove the washers fitted around the bolts.
Wrap the threads of each bolt with a single layer of sealant tape. Sealant tape strengthens the bolts without changing their shape, meaning they can easily be fitted back in place.
Place the original washer and then a new plastic washer on each bolt. The additional washer should help firm up the fixtures and prevent future creaking.
Affix the nuts and bolts back in place, and tighten with a wrench. Place the box spring and mattress back onto the bed frame. Lie on the bed and apply pressure to the bed to see if the frame still creaks.
Remove the mattress and box spring and take the bed frame apart again if the creaking still exists.
Put pieces of soft cloth at each point where the bed frame connects to wood or another piece of metal. The fabric will help to muffle any additional creaking.
Apply a lubricant oil to the nuts and bolts that hold the bed frame in place. This will moisten the fixtures and reduce the risk of future creaking. Reassemble the bed frame and place the mattress and box spring on it.