Act Confident and you Become Confident
When in doubt, act as if. Acting confident will make you seem confident to others. It is funny how that works, but when you act as if you are a confident person, it has the side effect of making you a more confident person. The same way that the act of smiling can make you feel happier, pretending to be confident will make you a more confident person.
Stand up Straight
The first body language signal you will want to send out is one of good posture. Stand up straight with your shoulders squared off and pushed back and you will show others that you are not afraid to be seen. It shows that you are comfortable in your own skin and that you are at ease being seen where you are.
What do you do with your hands?
One of the things people tend to worry about is what they should be doing with their hands. You should do what is comfortable, but do not fidget. Make very precise and slow movements. If you were to be all over the place with your hands, fidgeting and fussing with your clothes or hair, you will surely show others that you are nervous.
Maintain Eye Contact
Look people in the eye. Remember not to do the 'stalker stare' as that will make others feel uncomfortable. Maintaining eye contact is just another way of showing others that you are giving them your attention and that what they have to say is important. This will show that you are comfortable in the conversation and that will make you seem confident.
Take a few deep breathes and relax. If the situation is appropriate, you may want to put on an outfit that you feel good in. This will make you feel good about yourself and that is a step in the right direction towards feeling confident. Now go out there and put it all together... you may be surprised to find that doing these things trying to act as if you are confident will cause you to become a more confident person all around.