The earlier you add disractions to your training, the better.
This video shows Ziva learning to ignore distractions while heeling. At 11 months of age, Ziva's heeling is pretty good but the reward schedule is quite high. This is the best time to introduce distractions; while the work is still highly reinforcing and controlled.
When Ziva ignores a distraction, two things happen; she is rewarded by her trainer, AND I move the distraction away. The distraction (in this case, food), should be identical to whatever the owner is using as a motivator.
Adding movement makes this exercise a good deal more difficult. Ziva does quarter turns in heel position around me to practice adding movement. The most difficult move in heeling would be to heel directly towards the distraction and then adding an about turn.
This video shows the mistakes too. Food gets dropped. Timing isn't always perfect. That's ok. Training involves less than perfect sessions more often than not. Don't sweat it; dogs have a way of meeting us half way.
If you add corrections for looking away (even a verbal reminder), you're missing the point. Ziva must learn to choose to watch her owner rather than the distraction. It doesn't matter if it takes her five minutes to succeed; it must be her idea.
I think this is the second or third time we've worked on distractions with Ziva; it's time to start moving forward with regular distraction training. Ideally, she'll practice for two or three minutes a few times a week, slowly increasing the intensity of the distractions over time. Most dogs generalize this exercise fairly well, and soon you'll be throwing everything you have at the dog, and still they will maintain focus.
Try it. Just remember, it's the dog's choice that drives this exercise. If you can let go of control, the dog will take on that responsibility. I know; sometimes easier said than done.