Use postive training methods such as treating your dog every time he/she does the requested trick. To get your dog to 'sit' take a treat and drag it over his head in the air towards his tail as he/she looks up he/she will sit. Say 'good boy/girl' and use treat.
Use positive reinforcement with food and praise. Be consistent and use the same word for sit, down, etc. Get the dog to sit while saying "sit," give a treat and praise when successful and say "good sit. "
The most sufficient way is to reward the dog with treats and praise. If you position your dog and teach them what you want them to do they will catch on after awhile. Once your dog seems to be catching on you have to make sure to reward them. Even if they dont do it perfectly.