How to talk confidently

How do you talk confidently?
In my experience, whenever I am sure of myself, I get my earnest face on and speak about what I know I would. For example;

Girl: Can you cook?
Me: *looks her straight in the face* Absolutely.

Now I'm not saying you should lie about what you know you can't do, and I'm not saying you should be arrogant about it.  Just be sure of yourself when you speak, don't look down, don't care what the listener is thinking or will think. TALK!

If you don't look down, or scratch the back of your head before you speak people will know you're sure of what you're saying. You have to speak smoothly while you speak as well, else people will think you're trying to lie your way through a sentence.Don't talk too much, instead, economize your words. For example; this example is a lack of confidence in one's words

Girl: Can you cook?
Boy: I can make a sandwich and some other things, I just haven't gotten around to the soup making part.

The girl will certainly know that this boy is trying to impress her with the little he knows.  A confident person doesn't try to impress with words, they don't need to explain their skills before you know how valuable they are. You don't ask a professional chef if he can cook, he'd probably reply with an "Oh please"  or "PFFT!".

Next time someone asks you a question to test your knowledge, don't say, just do.