Check all props you intend to use in your presentation.
Test any demo devices or products you need. Check devices for battery power. Will any devices require internet access?
Check any promotional tchotchkes you plan to distribute for sales presentations. Make sure you have enough for all the key attendees.
Make sure you have a survival kit: water, tissue, cough drops, etc.
Have business cards with you.
If lunch or refreshments are to be provided, confirm delivery, spread, and timing with the support staff.