If you show your dog something over and over again; always teaching him the same way, he will eventually learn it. This breed picks up information quite quickly; some tricks will only take a matter of a week or two to learn.
When you are teaching your dog, it is best to do so in a quiet area where there are no distractions. Make learning fun, act excited when he learns something and never scold him if he is taking time to catch on. When he does master a trick, be sure to reward your Chihuahua with a lot of happy words of praise.
When a Chi is first trying to learn and is putting in effort, do offer a tasty treat as reward... But don't worry about always having to give food as motivation. When you also give praise at the same time, after a while a dog will have an automated response... and at that time your smile, praise and the attention that your Chi receives will be all that is needed for him or her to want to keep performing.