How Often
The answer to the second consideration is ‘not too often.’ A dog’s coat needs the oils produced in the skin to remain soft and silky and to keep from getting brittle or damaged. If you bathe your dog too often (every week, for example), you will strip away those oils.

A good rule of thumb is to only bathe your dog when he is visibly dirty or noticeably smelly. At the same time, you don’t want to go too long or a long-haired dog will tend to get tangles and matted hair. So the time between baths will vary from dog to dog and may change from one time of year to another.

How to Bathe
A few tips:

• Make it fun. Praise your dog often, and start while your dog is young so he gets comfortable with it.
• Select a location based on breed size and time of year. A sink or a washtub works just fine for puppies and small dogs. Big dogs need the bathtub. If it's warm outside, use a child's wading pool or a hose.
• Put a rubber mat in the bottom of your tub. Your dog will feel more secure.
• Before starting, gather all the things you need: shampoo, towels, possibly a bucket. Don’t turn your back on a wet dog unless you want to be involved in a chase.
• Make sure the water is lukewarm.
• Apply shampoo that has been formulated specifically for dogs. Use tearless dog shampoo products if possible.
• Wet your dog’s head last as that will minimize his desire to shake.
• Rinse well. The flaky, itchy discomfort many dogs experience after a bath comes from inadequate soap removal. This can also be caused by too-frequent bathing.
• Be careful when rinsing that you don't get water in his ears or eyes.
• In the winter, keep your dog inside until dry. A blow dryer, set at warm or cool - not hot - to avoid burning, can speed things along.

Dogs love a good shake to remove excess water. A shake starts at the dog’s head, so if you hold his head still, shaking will be limited. Tossing a towel over your dog immediately after the bath is done can prevent too much water on the walls. If you want to avoid getting an unwanted shower entirely, teach your dog to shake on command. This takes a little patience and training, but it’s possible. Once you’ve completed the bath, put your dog in a sit/stay. If he starts to shake, quickly guide him back into his sit. Resume sit/stay and get out of the way. Tell him to shake and praise, praise, praise.

Also:
Bathing is a good opportunity to check your dog’s skin. Feel all over for lumps or rough areas. Contact your veterinarian if you find any.