Dogs want to please you, and positive reinforcement is a powerful way to make a dog want to repeat behaviour.
Praising your dog sounds simple, but you have to follow some guidelines to make sure it is effective.
Timing is important. Reward the dog within seconds of the behaviour in order for him to associate that behavior with praise.
If you make your dog sit, and then wait until he is standing to reward him, he will associate the praise or treat with standing, and not sitting! Praise him as soon as his rear touches the ground. Keep your commands simple. Use one word where one is enough. "Off" is better than "Get off me" or "Get off the furniture."
Other popular commands are "Sit", "Stay", "leave it" and "down" (lie down) and "heel". Be consistent. That means everyone who handles your dog should use the same commands and reward the right, desired behaviour.
You can use positive reinforcement to teach your dog the commands, for example making him sit each time he asks to go out of the door, or to sit before he is petted, so that he is rewarded by his actions. Be careful not to reward the wrong behavior - don't let him outside every time he barks at a noise!
Dogs can be easily motivated by treats, and you can experiment to see what works best for your own dog. Be wary as if you overdo the treats, they will lose their effectiveness, as well as being detrimental to your dog's health. Work out what your dog likes best. Some dogs enjoy biscuits and others dehydrated liver pieces.
Begin by using a food reward four out of five times, and then gradually reduce the treats so that the reward is only occasional. Don't do this too quickly or your dog may become confused. Use a variety of treats and always combine a food reward with verbal praise. You may find your dog prefers a toy or play session to a food reward.
Soon you will no longer have to always carry treats with you, as your dog will be working to receive your praise, and knows that he might just get a treat as well.