Sit in the car, be calm, take some time to set yourself ahead of entering reception.
Put on a clean suit. Wear it sharp and clean.
Do not use unprofessional terminology.
Make first impressions count and offer warm greetings with all you speak to.
Try not to oversell who you are.
Suggestions for those looking for employment:
"Set up jobseeking toolkit and craft job search smarts. As soon as your chosen career paths are picked out, a CV and application letters can be crafted to reflect your merits so they correspond with the requirements of possible companies."