If you think of yourself as a sporty person, you are more likely to eat well and exercise, because after all, that's what athletic people do (as opposed to binge on ice-cream while watching Netflix in the couch).
I think the same principle can be applied to people management.
So here's the trick: Just describe the kind of person you want someone to become. That description will cause people to update their own mental model of themselves, and in turn, enact a positive change of behaviour.
For example, if you see some above-average writing skills in a person, tell them what an excellent writer you think they are. Probably that person haven't really consider “being a writer” as part of their “persona”, but now you've created a connection in their brain that will remember how good it feels to be praised as a good writer, so they will do it more often. It's all brain chemistry after all!
In short: help people believe in what they can become rather than tell them what to do or how to do it. So do tell them: “Wow, you're getting really fit!", instead of “you should go the gym more often”. Eventually, they will find out what they have to do to fulfill the expectations you've created.
Obviously, don't lie or paint an unrealistic picture of people's skills. This trick only works for positive traits that you want to reinforce. Do not ask the impossible, but by all means nudge people in the direction you want them to go by putting their skills in front of them.
Identify the potential in your people, tell them what you've seen and wait to see magic happens.