Take the mattress off the bed and shake the frame back and forth a bit to determine the source of the creaking. Tighten up loose screws with a screwdriver; insert washes between loose bolts and nuts to help minimize the noise.
Lubricate areas of the bed frame that may be responsible for the creaking. Use an oil-based lubricant on the joint areas of a metal frame. Brush wood oil onto squeaky wooden slats of a wood frame.
Sprinkle talcum-based baby powder onto the joints of the bed after lubricating the areas to muffle the sounds.
Encase squeaky wood slats with lightweight cotton batting. The material acts a sound-proof insulation that should reduce the creaking after replacing the mattress on the bed.