1. Practice exhibiting confidence through your body language
There is much evidence pointing to body language as a path to developing self confidence. A 'fake it till you make it' approach can actually generate confidence. So stand up straight, don't slouch, don't look at the floor. Pull your shoulders back, push out your chest a bit and keep some space between your feet when you stand.
Also, don't touch your face when talking to others, this is a clear sign of a lack of confidence, don't play with your hair or look anywhere but at the person you are talking to.
Smiling is powerful. It makes others realize you have it good, that you are relaxed and content. Smile and let it show in your eyes. You'll see it not only makes a big difference in how people relate to you, but it also, makes you feel better.
3. Make eye contact and keep it
Don't be the first to look away. When your eyes meet another, hold the gaze, especially if you or they are talking. Don't stare, just move your eyes to theirs and hold, let them drop to the face and then back up. Don't break eye contact quickly, people who immediately break eye contact give the impression that they either feel guilty for something, don't trust the person or are bored.
You can practice this with random people, and you may be surprised at their reaction when you get the nerve just to look them in the eyes. It will transmit confidence and interest.
4. Don't fidget
Compulsively moving your foot or nodding as someone else is talking transmits a lack of calm. To develop your self confidence, you'll need to be aware of your body and keep calm. If you feel yourself start to fidget, take a deep breath, disconnect for a moment and count to three. Then release your breath and return to reality in control of your body.
5. Listen to others
When you are talking to another person, listen to them intently, don't cut them off and don't start talking immediately after they are done. Take 3 seconds to process the information, and then formulate a response that is quiet and shows that you really listened. Use specific details if possible. The time you take to think and process what the other person said will make you look more confident, wiser and kinder.