The best advice I have ever read on the subject is in Dale Carnegie's "How to Win Friends and Influence People" (1936).

1) Become genuinely interested in other people.

2) Smile.

3) Remember that a person's name is, to that person, the sweetest and most important sound in any language.

4) Be a good listener. Encourage others to talk about themselves.

5) Talk in terms of the other person's interest.

6) Make the other person feel important – and do it sincerely.

So essentially be genuine, and if you try to do anything intentionally just try to put the other person at ease.