There comes a time in every dog's life when you can't escape the inevitable conclusion: he smells. In fact, he smells really bad. When you know the dog is entering the room before you see his furry body amble through the doorway, action must be taken. Yes, Rover, it's bath time!
As doggie caretaker, keeping your canine clean is your responsibility. Unfortunately, you may dread bath time almost as much as Rover does. The good news is that not all dogs need to be bathed particularly often. In fact, bathing a dog too often can be bad for his skin because it strips off the protective oils. The frequency of bathing depends a lot on your dog. Some dogs just get stinky faster. For example, retrievers and other water dogs generally have oily coats (to repel water), so they get a case of doggie odor more quickly than some other breeds. Short-haired dogs and dogs that spend a lot of time inside also generally need fewer baths than long-haired breeds or dogs that love to go outside and roll in disgusting things. Your nose will tell you how often you need to bathe your dog.
Before you wash your dog, brush him. Removing all the loose hair and mats makes the bath easier on everyone. Obviously, you have to wash less hair, but also on a long-haired dog, you are less likely to have matting problems if the dog has been thoroughly brushed out first. Water tends to turn small tangles into mats and small mats into big mats. If your dog has twigs, straw, or other pieces of crud in his fur, remove them. Clip out anything sticky like pitch or tar using clippers.
Once you have decided that yes, today is THE day, you need to get your bathing supplies together. Get everything you need in the bathroom before you go find Rover. The most important thing you need is dog shampoo. Dogs' skin is a different pH than peoples' so it's not a good idea to use human shampoo on a dog. You'll also need a lot of old towels. The bigger and hairier your dog, the more towels you need. Ideally, it helps to have a hand sprayer and a bathtub tether to hold Rover in place.
Once you have Rover in the bathroom, close the door. After you have him in the bathtub or shower, begin by thoroughly wetting down his fur. Follow the instructions on the bottle of shampoo, especially if you are doing a flea bath. Generally it's easiest to work in the shampoo if you water it down with some water in your hand first. When you are done soaping up the dog, move to the rinse cycle. Rinsing is extremely important and generally takes at least twice as long as the soaping up process (that's why a hand sprayer is very helpful). You don't want any soap residue left because it can irritate your dog's skin.
When the bath is done, the dog will inevitably shake. Probably all over you. If you can, it's nice to have the dog do one really big shake while he's still in the shower or tub (but if not, be ready to wipe down your bathroom later -- remember you did close the door, so he shouldn't be running all over the house). Then towel dry the dog. Most dogs love this part and forget all about the indignity of the bath. (Okay, maybe not.) Keep Rover out of drafts until he's completely dry, and then revel in the joy of a clean hound.