Because it makes you look more human and can help people identify with you.

You can start by sharing your struggles and failures, but don't fall for the trap of sitting around complaining about your job.

Don't overdo it. Insert the small funny stories that happen in your life in conversations.

You can keep a journal of your funny stories so you can use them later in a conversation or presentation.

When you’re talking to someone, everything else should be put on hold. Put your phone away and avoid looking at your computer screen if the person visits your office. 

And if you’re expecting a call, say so before you start the conversation.

• If you usually use your hands when you talk, be careful to match your gestures with what you're saying. Your hands should add meaning to your words.
• If you’re not a person who talks with your hands, that’s okay, too. Drop them to the side.

This is a good way to assert control.

Avoid looking down. It may indicate either aggressiveness or shyness, depending on how long you stare down.  In both cases, it is not inviting.