It is easy, it is a small gesture and the pay-off is huge.
Greet your students, invidually, before you start a class.
When they walk through the door, make eye contact, greet them, call them by their name, and genuinely let them feel welcome.
The impact of this is hard to measure, but very striking.
They are more engaging, their good will goes up, they take more initiative, are less afraid to speak up, and are more willing to listen to what you have to say.
The key is of course to genuinely mean it and not just use it as a manipulative trick.
This is just one thing you can do in a larger strategy. The larger strategy being, show them you sincerely care about their unique personality and presence.
The secret ingredient to effective teaching with long lasting postive impact is Love.
That may sound very hippie-ish and suspect and corny, because it’s spiritual, but if you try it, you will see people start to blossom like they are on healthy steroids.
More and more pedagogy related sites are promoting this habit, see http://www.brilliant-insane.com/2015/02/building-rapport-with-students-10-reasons-to-greet-them-at-the-door.html