hey bro'
i've been the best in like 3-4 weddings, you need to just be honest. first thing to do is to get the crowd the clap and thank the families for putting on such a great event, next thank the groom for giving you the honor of being his best man and how much it means to you, than tell a funny story about yourself and the groom, something that will relate. then tell him how happy you are for him and his new wife. i never really did written speeches just shoot from the hip. have a few drinks first it will loosen you up
good luck!!
post an update as to how it went.
gr