The key to training any animal is patience and consistency. You must also be careful not to reward all behavior and only good behavior should be rewarded with a small treat or love. The Jack Russell is a very energetic but loyal breed. Making lots of time to play with your puppy will create a strong bond and training will naturally be easier.
All animals can be trained through patience and consistency. Rewarding good behavior will promote good behavior, and the same is true of simple training tasks like potty training and obedience. For example, if you wish to train them to heel on a leash, you must first say the command then show them the meaning of this command. When they successfully heel as you walk you can stop to give them a treat. This is repeated several times. This is where patience comes in handy. Consistency is also very important. If they get treats just because they can be so cute when they beg, then they will not try very hard during training lessons.
The Jack Russell breed is energetic, meaning you will need extra patience when training them. The temperament can be different with a mix, so you will want to research the other breed for temperament and specific skills.