If the bottom bracket squeaks or creaks while pedaling, the mechanism might need to be pulled out of the frame, cleaned, along with the bottom bracket shell, and re-greased. If there is no play in the crank, manually derail the chain so that the cranks can spin freely. Just like checking the hubs, see if they spin without grinding or odd vibrations. It's time for the final step, checking the headset. While straddling the bike upright, engage the front brake and wiggle the bars forward and back, in as straight a movement as possible.
Any perceptible play means the headset needs to be tightened.
If there is no play, raise the front wheel off the ground by holding the frame with one hand. With the other hand, tap the bars, turning them left and right to check for any restriction. If it doesn't turn freely, the headset may be too tight. If the headset seems to get stuck in certain positions, there's more than likely damage, and it will need to be replaced. There are two nuts that secure the headset.