There is a huge power in preparation. It gives a huge boost of confidence, gives you ideas to give more suggestions during the interview and ask questions no one else asked.
“If you keep putting unbelievable quality in, when it's time for you to cash that spiritual, emotional, physical, financial, or business check, it ain't gonna bounce, because you've been making deposits, and you've got plenty to give.”
Spend a lot of time to prepare before meetings and presentation.
If it’s something important, spend at least 18 hours preparing. This is how much Tony Robbins do.