Where to Reinforce on the Go Out

"It depends"  on which part you are working on. These are not the only option and possibly not the best options... but they're  my current favorites.

Looking ahead while at heel:  Release and toss reinforcer forward

Initially leaving your side:  Send and toss reinforcer ahead of the dog, prompting chasing before getting the food toy.

Running out while further away:  Send and have a helper toss a toy out even further ahead of when the dog is at the "far" point.  Or you can try and toss. But only toss if the dog is looking ahead. And monitor to be sure that the dog isn't looking back to you.

A sharp turn back:  Toss the reinfocer in a way that encourages more of a turn after the dog starts.  Griffin turns clockwise, so as he turns to face me, I toss the toy behind him, to my left. 

A sit that creeps forward:   Behind where you want the dog (practice with ring gate posts but not all the fencing so that the dog doesn't have to jump the fence to go get his toy/treat).  

The launch back after the sit:   Release from the sit, toss the toy in the direction the dog is to go.

The duration/stickyness of the sit:  Run in and feed or play...  gradually adding in duration. Same thing can be done with then tossing away, but if the duration is really a problem, it's best to be reinforcing in position to get the behavior more 'sticky'.