I have chosen two recall commands being "Come" and "To Me". The "Come" command is my emergency command. Every time I issue that command Kassa gets the most tasty of tasty treats. I always want to have a treat in pocket when I use it because I don't want Kassa to get into his head that he may or may not get a treat. In other words I don't want to dilute the command. "To Me" on the other hand I use more regularly. I try to make sure that Kassa gets some sort of reward with that command. It may not always be a treat. Sometimes I throw a ball for him and sometimes it is just praise, although I try to make sure he never associates it with anything negative. I have used it in the dog park when people are letting in a dog that I am not yet sure about or that may be too small. I can't use treats there because treats aren't allowed in the dog park but when training it I will throw a ball. I try to train both these commands indoors and out and in a variety of settings. This way Kassa wont get into his head that he gets a treat when I'm sitting on the couch in the living room and he is on his bed ... and nowhere else. I also try to mix up the training. The commands may come in the middle of a game of fetch.. or before or after.
I try to vary the distances he has to travel and even make it a bit of a game when we are inside. He goes from garage to the second floor of the house to try to find me. When I use either command I try to touch his collar. In case of emergency I don't want him to come to me only to trot away as I reach for him.
A big open area is a great place to train recalls because it provides a lot of distractions. There are many things to sniff and explore.
Kassa and I just got back from a training session. He was in the other room getting some water. I played the video on my camera to see how it came out. He heard my command in the camera and came running. I got up and gave him a treat.