Body Language

Understanding body language and the signals you send off can help you quite a bit. If you learn from your natural tendencies you can avert any possible wrong impressions you send off subconsciously or unintentionally. Unintentional signals that give someone the wrong impression are the worst as they can derail you without you even knowing why or that it even happened.
The best source for this is an illustrative book (in my reading list), but I can give a few general tips that should help you right off the bat.
Now, once you understand body language and the physical cues that it gives, learn to use it to read people. Some are more readable than others but what you can observe may help you to see what is thought or felt but not spoken. Want to know what the other person is thinking about your ideas or simply what they think of you, just watch them. Develop this skill and you will be amazed at how well you can read someone in almost any situation.

1. The Hand Shake - Arm extended, palm up and a firm but not an Olympian grip. Look the person in the eye and smile. Shake, don't just hold. That's just creepy. A handshake conveys confidence in dealing with people. It can also convey the amount of importance that the other person ranks you as, it makes the statement: If you are not important enough to impress why should you be important enough to listen to.
2. Smile. Smiling is always good. When you greet someone or pass them in the hall if you are always preoccupied with your next move and not focused on the person passing you the absence of an enlightening smile may send the message that you are unhappy or frustrated. Smiling is your most powerful body language signal and it comes for free. Though it is not recommended to smile constantly (people will be under the impression you are searching for approval or just plain weird), you should still make an effort to appear happy and optimistic.
3. Be very conscious of your facial expressions. When a bit of bad news comes, try not to react through facial expression, rocking your head side to side, outwardly sighing or the "rubbing your face stance". In fact, leave your face alone, don't touch it. People see these and learn to read you or take the que that something is very wrong. You also come off as frustrated. Unless this is the message you want to send, avoid it.
4. Mouth movements can give away all sorts of clues. We purse our lips and sometimes twist them to the side when we're thinking. Another occasion we might use this movement to hold back an angry comment we don't wish to reveal. Nevertheless, it will probably be spotted by other people and although they may not know the comment, they will get a feeling you are not to pleased. Again, a good move if you want to convey it, a bad move if you are playing poker.
5. When making statements or giving commands don't look (dart your eyes) to your superior or others in the room for support. This makes you seem unsure and that you are looking for approval.
6. Don't cross your arms when talking. This is an aggressive stance and sends the message that you are uncomfortable. The same applies to your legs.
7. When you want to convey the impression that you are interested in a conversation or discussion, lean into or toward the person you are conversing with. Angle of the body in relation to others gives an indication of our attitudes and feelings towards them and also indicates that you feel safe and not threatened. We angle toward people we find attractive, friendly and interesting and angle ourselves away from those we don't, it's that simple!
8. Don't fidget.
9. No clock watching unless you wish to convey that your time is more valuable than your audience or you wish to send the message "Hurry up".
10. Don't stare. At anyone (creepy) or anything (is he lost?).
11. When someone comes into your office to talk to you, stop typing at your computer and look at the person. There is nothing more irritating than having a conversation with a person who's typing on their computer at the same time. This body language tells your visitor they really aren't important enough to focus on.