When it comes down to it, bathing a Poodle is just as important to the overall grooming process as is brushing or clipping. Poodle hair is much more similar to human hair than that of other breeds, so it needs to be washed more often; plus, the dog's skin constantly releases a bit of body oil--and after 2-3 weeks that oil will clog skin pores and begin to stink. (Anyone who's ever wondered why do Poodles smell, that's the reason.) A regular Poodle bath will both clean the hair and wash away those oils.
Though opinions differ on what's the best Poodle shampoo and conditioner, the All Poodle Info site has a page dedicated to the best shampoo for Poodle dogs. Regardless, make sure the shampoo is formulated for canines, as the human kind can severely irritate a dog's skin.
If your Poodle is Toy or Miniature, you can do the dirty Poodle bathing in the kitchen sink; Standards can be bathed either in a bathtub or in an outdoor kiddie pool using a garden hose.
Here's specifically how to bathe a Poodle: first give the coat a thorough brushing, then wet it completely. Apply a small amount of shampoo to the dog's back, then lather well, working downward. (Don't forget the legs, underbelly, and tail.) Use a washcloth to clean the Poodle ears, head, and face, then rinse thoroughly. Repeat the entire process with Poodle conditioner. Last, dry the dog using two steps: first with a towel, then with a blow-dryer, using a brush with the dryer to keep the hair in control.
Another often-forgotten aspect of grooming: Poodle ear cleaning. Actually, though, learning how to clean Poodle ears is simple: use a cotton ball and a gentle cleansing solution to wipe out the surface inside the ear flap.