I've found with Diva the two stick method works best. Throw one stick. When she comes back, she sees the other stick in my hand, I wait until she drops it (I usually use "drop" as a command) She'll drop it usually within a couple feet of me and then I throw the second stick....and repeat. With one stick she'll bring it back and then it's a game of keep away.Cute photo!
My 6-month old will sometimes choose a stick rather than her toys, when we are playing in the yard. We need to work on the "give" command. Can't play fetch, if she won't share.