The 1-2 punch combination is a basic but highly effective boxing combination to use as it is fast, powerful and doesn't expose you to counter punches that may get you into a bit of trouble.
It's very commonly used by boxers and is a great way to set up a bigger punches like a left hook to the body or jaw.
Step 1: Perfect Your Jab
The jab is meant to create a clean set-up shot for a powerful right hand.
A lot of beginners throw jabs that rotate their body too far over which crosses over blocking their right hand.
This will require more work to move back into a position where you can throw a right hand punch.
First and foremost, make sure you are in the position to throw your right hand and then jab from there without messing up the position.
Remember to not jab in a way that takes you out of your right hand position.
Step 2: One Shot That Hits Twice
Try to imagine that the 1-2 combo is one shot that hits twice.
Keep in mind that each shot needs to be clean and not overlapping over each other.
Let us know how you go implementing these tips.