I started asking the girls...do you have to potty? and then would take them out.
In the beginning when they went outside they got a treat immediately.
The entire time we were out there I would say. "potty outside".
Bella is big enough to use the doggie door. But, Piper is not even 4# so i wont let her run outside alone.
I say do you wanna go potty outside and she goes nuts! She starts dancing around and scratching at the door.
Now sometimes she will go to the door and look at me. If i dont see her she walks to me until i look at her and then I usually know.
I found one piece of advice helpful when i was training my girls.
Potty time is potty time..try not to mix in play time.
Let that be another adventure
Good luck!