I don't know if I can help, but I'll try. I use 3 different commands. To me, "Leave it" means to leave it alone. No matter what it is, it isn't to be investigated. This came in very handy when we found an injured porcupine on the side of the road. And here I thought teaching him to ignore poo was a big deal. Great command!
I teach "Drop it" too, which means whatever's in his mouth gets released. This command gets used when we're playing with the flirt pole, since the game is pretty much all about chasing the toy, and that won't happen unless he's dropped it. Another very useful command.
For retrieve games, I use "Hand" as in 'hand me the object.' I taught him this by playing with a larger frisbee - one I could hold at the same time as he had it in his mouth. Before I started using this word, I had already taught him to bring back the frisbee and "Drop it" at my feet. If he dropped it anywhere else, I'd tell him to go get it. That was more patience than anything, and I never chased him down for the toy. He learned that the game continued when he dropped it at my feet.
Then I added "Hand" when he was 100% with the dropping at my feet. It was a smooth transition for him, as I held the frisbee he naturally released it - he wanted that thing thrown, lol! So I added the command as he was releasing. Ta da!
The hardest part is being consistent. He has toys all over the yard, and he'll do his best to drop a toy and bark for it to be tossed for him. I have to continually tell others not to reward the bark, and ask for "Hand" if they want to play together, lol.