No matter which type of training you want to begin doing with your Chihuahua, there are some basic elements that should be understood and set up in advance. These will help guide you to fast results.
Your attitude, as a trainer, is vitally important.
Your Chihuahua will be the student and you will be the teacher. And your dog will learn much faster if you are patient and enthusiast. Your Chi will take cues (verbal and non-verbal) from you in regard to how he should approach learning something. Is being in 'school' something to dread? Or is it a challenging yet rewarding experience?
Consistency is key.
This is one of the most important elements. Dogs have rather short-term memories, yet they can also remember things for years with fantastic long-term memory. The key is to do sessions as much as possible. The repetition will help move the information from short to long-term.
Training hardly ever works if you do it 'sometimes' or even 'most of the time'. If you are serious about training your Chihuahua, stay strict in your routine. When house training, follow the guidelines exact. When command training, do two sessions per day. When heeling, do this every single time your Chi is on leash.
3. Reward and praise.
Dogs need to know why they should do a certain action. Yes, listening to their human is a good reason; however, when it comes to learning new things a dog does best if he is motivated. The best way to motivate a dog is to instantly mark correct behavior or action with a tasty treat. Don't worry; once your Chi is doing well the treats can be phased out and only given now and again as positive reinforcement.
And dogs soak up praise. When a Chihuahua is told that he is doing awesome, he'll gain self-confidence and be more prone to repeat the behavior.