Use your time in front of an audience to captivate them, and then, when you leave... they won't wanna see you go.
Also, if you're a politician, promise them lots of shit that won't actually get done, and THEN worry about the excuses for why. Some good ones are 'The (previous administration's name goes here) set into motion certain policies and practices that...', 'The (opposing parties name goes here)'s are blocking legislature that would enable us to....'
... blah blah blah, you get the idea. =)
Just go up there, smile, be yourself, and really OWN the crowd. All eyes SHOULD be watching you... make sure that they are. =)