Recently, two different friends talked to me about motivating their project partners.
Friend: "I want my partners to work hard. Does this mean I have to work longer than all the rest of them?"
Me: "No, you just have to set clear goals. If I told you that tomorrow we might go on a run, you wouldn't be sure how much to prepare, so you'd watch me and follow my lead. But if I told you that tomorrow at 10am, I'm coming over to get you and then we're running 5 miles, you'd drink water and go to bed early. No matter what I'm doing, you'd be stretching and getting ready on your own."
Friend: [agreeing noises]
Me: "Being clear makes it a lot more motivating. If I told you that we're running 5 miles at 10am, it's very likely that we'll do it. If I just said that we're running tomorrow, we'd look up at 11pm after a day of playing Starcraft and say, 'Weren't we supposed to go running today?'"
Friend: "LOL true."