Eye contact and a sincere smile can get you almost instantly a great rep with a new person.

They try too hard. This has been discussed over and over again, but my take on this is that people often try too hard to explain themselves to others in efforts not to be taken wrong. This often irritates the listeners or kills what was already a pretty lame joke.

When you make a statement, make it a statement. If you have to keep beating the dead dog explaining it for people to understand it, it's probably not a very good statement.