Clear away any items from the bath area such as soap, shampoo, and wash cloths.
Wet the bathtub by running the water for a few seconds. While the water is running, wet one of the cotton wash cloths.
Squeeze a teaspoon or two of dishwashing soap onto the wet wash cloth. Begin scrubbing the bath tub with small circular motions, paying special attention to curves where grease and dirt tend to collect. Add more soap if necessary, and remember to clean ledges, soap dishes, and the faucet.
Completely rinse the suds out of the bathtub. Rinse your wash cloth out several times and use it to wipe areas that cannot be rinsed by the stream of water. Once you have completely rinsed the tub, double-check to make sure you didn't miss any spots. If you did, repeat Step 3.
Once the tub is completely rinsed and suds-free, spray it with Windex or a similar glass cleaner. Use the other wash cloth, which should still be dry, to wipe the entire bath tub. Your bath tub should be sparkling clean. Replace the shampoo and soap.