Well, one can write an entire book on this. Also there isn't a definitive answer. But, as you say, here are some "tips and tricks":

• make it clear that you're on "their side". That you're helping them to make the shoot good.
• arrange a little their clothes, their hair, take an invisible piece of dirt (it doesn't need to really exist) from their clothes - this helps to break the distance between you and them
• talk to them. Make them speak. Jokes. This will help them to be natural.
• praise them. Say 'Wow!', 'Great!', 'Very good!' etc.
• do play with them. Make them play.
• put music. Good music. (Well, what means 'good music', this is another story...)
• say to them "I'll take now some shoots but don't be afraid, I just check the settings, camera, metering etc. I will take the official shots latter". This will make them more relaxed.
• give them indications but don't tell them too much how to pose. Rather show them by your example (your body, hands, facial expression etc.)
• give them something in their hands or show them how to keep them. Usually people doesn't know what to do with their hands.
• take great care to not be 'boring'. Neither you, neither your session.
• be innovative. Try to push the envelope on some shots (even if they'll be thrown away - you'll see that these will be one of the best) just in order to keep the things 'interesting', 'fun' etc.
• have your attention focused on your subject's mood. He is the most important thing, not the camera
• smile. be professional.
• be humble.