My favorite myth about positive reinforcement training is that using treats is bribery. I am very careful to make sure my clients are not holding the treat in front of their dogs face and asking for a behavior. Treats before behavior is bribery, treats after behavior is training. I like to reward effort in training so how do we know when to move away from constant reinforcement.
The 80% Rule
If your dog can perform the behavior immediately, when asked for the cue 80% of the time, you can start backing off reinforcing every single time you ask. The rule here is that everything else has to look the same. If you change the picture at all, back to rewarding every time. If you change the location, distractions or ask for duration in the behavior, you have to go back to rewarding every time. Then when your dog gets to 80% you can back off rewarding every time. Note: this does not apply to your recalls. Recalls get rewarded 100% of the time forever! 
The Sit Test
One of the ways to evaluate how much effort your dog is putting in is to ask for something super easy like a nose target. I teach a nose target because it is such a cheap and easy behavior for your dog that it becomes a great way to see where your dog’s brain might be.
When I get to the outside lesson with my clients, the training plan usually looks like this: We leash up and go to the front door. Can your dog nose target? Can he sit? Yes, we open the door and move one step outside. At this point, the dog has hit the end of the leash because they have learned the faster they get out the faster they can get home. Outside is scary and we might die. I stop the team and we wait. Now the dog is forced to actually sniff stuff for the very first time. We wait at this point until the dog looks at the human part of the team, and we reward, and we wait. When the dog is actually paying attention to the human, we ask for a nose target? If we get a yes, we ask for a sit. If we get a no, we wait. I want the nose target and sit to look like it does inside the house before we move forward.
According to your dog, their brain is spent on making sure they aren’t going to die. Because up to this point they are pretty sure every walk is a death sentence and they will never make it home. At the very least they have forgotten you exist, and by stopping, you help remind them that they are fine and you are not going to let anything happen to them.
Increasing your Reward Value
It is amazing what happens when you increase the value of your reward. If your dog is working for kibble inside the house, what happens if you bring cheese outside with you? Is your dog more focused on you than the environment? Use that focus to help them explore a little farther, and work a little harder. Play with what your dog can do for a higher value reward vs kibble. As they get more proficient in the skills you can move back to kibbles.
Some dogs find some activities easy, and some seemingly easy activities very difficult. As a trainer working with dogs who have some behavior issues, this is one of the areas I have to explain to owners often. Some dogs find different places easy to handle, and some need a little more time to dismiss certain things. This is how we determine how your dog is feeling in an area, and figuring out how much effort your dog is actually putting into listening to you. Once you determine that, you can start to reward accordingly!