It's great to teach your dog that good things happen by looking at you, it's an important skill to have in your toolkit. Having eye contact on cue means you can ask your puppy to look at you and look away from all kinds of distractions.
Once your puppy learns that giving you eye contact is rewarding then they will start to give you voluntary eye contact as a way to access rewards and this when the magic happens, at this point your dog is basically saying they are ready to work and engage with you.
Take one treat, place it on your dog's nose then immediately move the treat to your forehead and say 'Look', as your dog looks up at the treat mark and reward. Repeat around 10 times.
Then hold a few treats in a closed fist and place them by your shoulder, cue 'Look' and wait to see what your dog does. If they look at you then mark and reward but if they don't look at you then you need to go back to step 1 and continue to use the lure of the treat to your head.
Play around with where your distraction food hand is, you are using the food in the hand to distract your dog from already looking at you because you want to make sure that when you cue 'Look' they orientate their attention back to you.
Practise this in lots of different locations.
Wait for it!
Have a handful of treats ready and your dog in front of you. Start in a low distracting environment.
I like to keep my hands behind me back, now simply wait for your dog to look at you, when this happens mark with a 'Yes' or click then reward with a treat. Repeat!
If your dog does not look at you don't be tempted to nag them, just wait.
Once your dog is getting the hang of it and they are consistently looking at you then you can add the cue 'Look'. Say the cue 'Look' just before your dog looks up.
To add another level of difficulty, hold some treats in your hand out to the side, this is to distract your dog. When your dog is looking at the handful of treats cue 'Look' when they take their eyes off your hand and look at you mark with a 'Yes' or click and reward with a treat.
Practise in lots of different environments.
Practise Makes Perfect!