Many people think rats don't need bath, but a rat should get a bath once every six month, and i'll show you the correct way to do so.
First you will need a bath tub, or sink remember to always have a plug in the drain, because rats down a drain is not good. Well fill the the bath tub with luke warm water only about two inches deep, or less.

Step 1: Rat

Gently place your rat in the tub, but remember to watch out, and where a long sleeve shirt and gloves, because rats don't like baths they will use your arm to claw their way out. Let your rat get used to the water before starting the real bath let them play around first.

Step 2: What to Use

You will need baby shampoo since any other shampoos are to strong, and could make your rat ill. I recmind Johnson's Head-to-toe baby wash it is nice, and gentle.

Step 3: How to Scrub

Be very gentle as you wash your little guy use only a teaspoon of soap, and gently move your hands back and froth, and use and thin tooth comb to brush it in. Then rinse it off with luke warm water make sure you get all the soap away. And never scrub your rats head avoid that even as you rince.

Step 4: Drying

When drying your little rat make sure you don't get their ears that can hurt your little guy use a circle mosion to dry your rat make sure your rat is all dry before putting back in his cage.
That is how you give a rat a bath!