Inspect the entire bed frame and look for any loose bolts or nails that have begun to work themselves out of the frame. Pound any loose nails back into the frame and tighten any bolts until they cannot move any further.
Sit and bounce on the bed to try to locate the squeak. Have a friend walk around the bed with a can of WD-40 or a similar spray lubricant while you bounce up and down on it. Every time the bed makes a noise, have your assistant spray the squeaking area.
Remove any bolts that produce a squeaking sound. Put a new plastic washer in each bolt if it does not already have a washer then tighten down the bolt. Replace worn metal washers with new metal ones.
Remove the mattress and box spring from the bed and examine the condition of the coils. Look for items stuck on the coils or under the bed that could be contributing to the squeak. Spray the coils with spray lubricant if they are the source of the squeak.
Reposition the mattress and box spring if the squeak is coming from that area. The mattress and box spring should be in the middle of the bed frame. If they are too close to the head or foot board, they can pinch together and produce squeaks.