You need to find three Helmets in singleplayer campaign of Duke Nukem Forever to unlock Bucket Head achievement or trophy. You can find below brief text descriptions alongside a video showing where you can find these Helmets in Duke Nukem Forever.
Duke Nukem Forever Helmet Locations Guide
Location. Start of Las Vegas level, just beside the soldier, who actually tells you to wear a Power Helmet.
Location. Load the hive and instead of going forward, go backward, take a right. Go through the weed enclosing the opening, and take a left. You will find a dead body, with second helmet.
Location. Load the under water level and go forward, plant the first bomb at the gate and use the wheel, go further ahead and you will see a blinking light, follow it as it leads you to the helmet. You will enter in a small area with a dead end on the right. This is where you need to look for the helmet.
Duke Nukem Forever Helmet Locations
If you have found all three helmets in Duke Nukem Forever, you will unlock Bucket Head achievement or trophy. For Companion Barrel Achievement, check out Companion Barrel Achievement Guide.
Note. If you are facing any performance or graphics issues, you can check out Duke Nukem Forever Crashes, Errors, Freezes and Fixes Guide.