When I teach Elka a new trick, it happens for a variety of reasons. Sometimes it's because I see or hear about what another dog can do, and I think "Well, Elka can do that." Sometimes, some behavior she's already exhibiting is something that I wand to shape and encourage into a complete behavior.
Whether you're using a clicker or not, you need to have criteria. You have the finished product in mind, and have to have an idea of what steps you want your dog to correctly take in order to reach that product.
"Find it" is something Elka already knows, depending on the context. She knows the names of a few of her toys (Gumby, Pokey, ball, etc.) and I can say "Where's Gumby? Find it!" And she'll find Gumby and bring him to me. We in fact play the "Where's Gumby" game for some indoor fun; I have her down-stay in the kitchen and I hide Gumby in the living room, and then release her.
Then I heard about the Kyra Sundance Trick Dog title, and thought, "Well, Elka can do that." I'm confident she has Novice in the bag (and already have a willing witness lined up), and am more or less confident about the Intermediate, but thought we ought to brush up, and perhaps add some more. You can always add more tricks.
So, I saw the "Which hand holds the treat?" and thought it could be a different "Find it" context. To teach it, I have Elka sit, show her a treat, rub it between my hands, and then close each hand into its own fist, with the treat in one of them. She can sniff both hands all she wants, and lick; I decided that my criteria for the trick to be successful is for Elka to put her paw on the hand that holds the treat, as it seemed much clearer to me than just nosing or licking. Sometimes she will sniff the correct hand for a good long time before bringing the paw into play, but really, we've only had two sessions of it. Unless I have it in my teeth, I can't use the clicker for this particular trick, as both hands are already occupied, so I'm using "Yes!" as a marker for when Elka uses her paw correctly.