Summarize the following:
If you have any loofahs, soaps, or bottles of shampoo, conditioner, or body lotion, take them out of the tub. Place them on the counter or somewhere out of the way where they will be safe while you clean the bathtub with bleach. Turn the hot water on briefly and run a sponge under it. Turn the water off. Use the damp sponge to wipe down the surface of the bathtub.  This will help loosen grime and material, making it easier to eradicate tub scum later with bleach. Combine ½ cup (118 milliliters) bleach with 1 gallon (3.8 liters) of water. Dip a sponge into the solution and wipe it across the surface of the tub. Wait at least 5 minutes before moving on to the next step. After you’ve left the bleach solution on the tub for at least 5 minutes, dip another sponge in cool water and wipe the tub with it by moving your hand in a gentle circular motion. Wipe the tub dry using a towel. If your bathtub is still grimy, mix a paste of equal parts baking soda and bleach. Apply the paste to the grimy or discolored area. Wait at least 15 minutes, then spray water on the paste and use a damp sponge to wipe the paste away, moving your hand in a gentle circular motion. Dry the area with a towel.

Summary:
Remove everything from the tub. Rinse the tub out. Mix bleach with water. Rinse the tub again. Make a baking soda paste to scrub away tough stains.