Most people look at self-confidence as appearance. Someone will either appear confident or question their own abilities. This is usually fairly easy to pick up on. It is very difficult to act confident when you do not feel this way. This is one reason I always stress to act differently than you feel.
Self-confidence does not have to be about the clothes you wear or the way you talk. Self-confidence should be about you being open to change and growth and welcoming new ideas. It should be about you being comfortable to be uncomfortable. Self-confidence comes easy when you stick to your ways and do not go outside your comfort zone. True self-confidence will develop when you are willing to make alterations to your lifestyle and start to make progress. Just remember that you must always be confident.