It is very important that you have already trained your 3 month old puppy to sit, stay, come, go to kennel etc. Now your wish is to get the ideas on how to train him not to jump up on.
Some think that a dog jumps usually because he wants to come up to the same level as us. It is important to stop a dog from jumping because this does not suit well with his behavior.
So you can start training your dog by this way:
To begin to stop a dog from jumping, make sure that every time the animal does it, you look away and refrain from eye contact. Then, Command your dog to sit, and reward with a treat if he obeys. The aim is to let the dog know that he will be rewarded if he avoids dog jumps when greeting. This may bring success!
There are some books available written on the detail about stopping the jumping up of the dog. You may read this too!