Start training by placing a little dog toothpaste on your finger and let your dog lick the paste from your hand. Do this step several days in a row, and follow it with a treat reward and lots of praise.
Place a little of the paste on your pet's large canine teeth in front. This gets your dog used to having something placed against his teeth and gums. Do this step for several days, and again, follow it with a reward and praise.
Now introduce the toothbrush you will use for regular brushing. Place some dog toothpaste on it and allow your pet to lick it from the brush. It will get your pet used to the texture - and of having the brush near his teeth and gums. Praise and reward your dog, and repeat this step for several days.
In the final phase, you will actually brush your dog's teeth. Gently hold back your pet's lips and hold the brush at a 45 degree angle to the gumline. Brush the outside of each tooth, moving the brush gently back and forth. Talk to your dog in a soothing voice and always follow brushing sessions with a treat. Brush just a few teeth the first time, and gradually lengthen the session each time until you're brushing all the teeth.
When finished, be sure to reward him with lots of petting and praise. The rewards and praise will help him associate brushing as a positive, rewarding experience.
Ideally, you'll brush your pet's teeth every day - but at least a few times per week. If time is tight, give your pet's teeth a quick cleaning with dental pads. They kill bacteria on the surface, leaving his mouth fresh. With just a couple minutes of dental care per day, you'll go a long way toward preventing plaque buildup - and periodontal disease.