How I learned to combo tricks is by learning how to do more tricks. So basically take the time to learn how to do tricks and repeat them a lot and learn what joint are really important to use for the trick. Once you have learned different tricks, it will come naturally. It's kinda hard to explain the learning process for tricking but just keep practicing is the best advice I could ever give you.
Also take a look at the tricktionary. That has a ton of tricks on there and example videos of what the tricks are. Practice off those.