How to Train Your Dog To Focus Around Distractions
What's the best way to have a reliable recall? Stop your dog running off in the first place. I call that tricky little art "engagement" - and it's arguably more important than recall training but much less discussed.
Here's what we know for sure. What we reward happens more often. Therefore if we want our dog to stay closer to us we should reward them for that. But what are we supposed to do? Reward them whenever they're 1m away, 3m away, 5m away?
Unless you plan on taking a tape measure out we need something more specific. That thing is the 'Check-in', the moment your dog turns back and looks at you.
Now if your dog is in cloud cuckoo land whenever you go on a walk you might start by simply rewarding check-ins whenever they happen. I oftentimes challenge people with very unengaged dogs to do this for a week and the results are usually dramatic.
If you're a bit further into your training you might find your dog lacks engagement (and the ability to listen) only when there are distractions.
Now here is where engagement training becomes rather magical. You can teach your dog that the distraction itself is a signal to check in with you. 
I'm not meaning to patronize here. That seriously was a pivotal moment in my dog trainer development.
All of a sudden all of these distractions are actually signals for your dog to pay attention to you. The world just got flipped upside down.
Doing this is simple, with your dog on a 5m lead (here's what we use) when you're on your walk and your dog becomes distracted stop and wait. The moment they turn back to you, we say "Yes" and reward.
You might even reward with the "Go Play" signal if the distraction is another friendly dog. Teach this by waiting for your dog to turn to you, saying "Go Play" and releasing the tension on the lead so they can greet the other dog.
With practice you'll begin to get an immediate check in around said distraction. At which point you can decide what comes next - recall away or go play.