See every interview as a learning experience. Write down the interview questions and review your performance. Consider what went well and what you could have done better.
Write a thank you email to the employer. Thank them for seeing you and reaffirm your interest in the role.
Not many applicants do this, and it's one way of standing out from the crowd.
Usually an employer will get back to you within a week of the interview, unless they tell you otherwise. If you do not hear from them, you could call and politely ask how the selection process is going.
Should you be an unsuccessful candidate ask for feedback on your application and interview. Ask how you could improve your interviewing skills.
With experience you will be able to market yourself better, handle difficult questions with more confidence, and be more relaxed in interviews.