Afterwards: After the interview, send a thank you email to all your interviewers. Customize each one if you can, referencing the specific conversation you had with that interviewer, and adding briefly any points that you may have forgotten in the interview. After you have sent your emails, make any notes that help you to learn from the experience, e.g. adding some of the questions you were asked to your list of practice questions.
If you follow these tips, you will get better and better, and more comfortable being yourself and telling your story during the interview. This will translate into confidence visible to the interviewer, helping them to feel confident in the decision to hire you. Good luck!