Training your cat can be a fun and rewarding experience, but patience and time is something that will be necessary. You can train your cat to have good behaviors so that when you are away you will know they are safe.
Kittens are much easier to train than an older cat because a kitten is like a child and we have to teach them the right and wrong. Older cats are not so seasy to train, as they are set in their ways, but they are still trainable.
This book explains in detail how to go about training your cat for the most popular behaviors etc.