I used to hear this from my parents, friends, and school teachers. I still hear this until now, especially when I do something I am not used to.
I remember when I had my first job interview. My friends keep on reminding me that I should keep on practicing in front of a mirror, pretending as if my reflection was my interviewer. I did, and it helped me a lot to be composed and confident during the real interview.
Practice makes perfect indeed.
Here are several pointers I can share on how to practice before your job interview, which really helped me. Hope they will worked for you, too. These tips were actually intended for my sister, but I decided posting it here hoping that someone who is afraid of job interviews may happen to read this post ;D
1. If you're nervous about speaking up, practice with good friends, with a family member, or in front of a mirror.
2. While practicing, don't twirl your hair, bite your nails, or rock back and forth. Sit back straight. Relax.
3. Try to be professional and serious while having your practice. Pretend that it was a real interview and observe yourself.
4. If you practice with a friend or a family member, ask them your points of improvement, and then work it out.
5. Watch the local news and observe how the anchor talks. Try to imitate her or him, but not too hard.
Most importantly, while having your "real" interview, remember these:
1. Before entering the room, breathe deeply. Relax.
2. Look the interviewer in the eye.
3. Hold your head up with confidence.
4. Avoid mumbling and saying "um" and "uh" when you speak.
5. When you state your answer or opinion, speak clearly, calmly, and confidently.
Good Luck!