Originally Posted by Charlie W
While she's pottying repeat the word that you would like to use as the command to go potty. Praise when she's done. It's really useful to be able to tell them to go sometimes, I do it if I'm meeting a friend for coffee out somewhere and I don't want them needing to go while we're there! Also useful last thing at night when it's cold outside and I just want them to go to the toilet and come in again without conducting their usual border patrol!
Pretty much this.
Emptying their bladder is reinforcing enough it isn't really necessary to praise it except I guess to show approval for their choice of spots to do it vs them doing it inside or something.