This has worked for me in the past. Advertise, (don't apologize) and a little joke is a good plan. They know you stutter, so that cat left the barn. Don't be afraid to stop and reset yourself if you need to. Take a breath and/or a bit of water (more than just a sip, make your mouth/throat do something else). Take your time, know your topic, and a buttload o' good luck!