I was my brother's best man.
When in doubt:
1) Thank everyone for being there.
2) Thank both sides' parents.
3) Compliment the beauty of the bride.
4) Lightly roast the groom.
5) Bring it all together with how much they're meant for each other.
6) Raise a glass.
7) ??????

Profit [impregnate a bridesmaid]
I read this tip from here a few years back.
If your speech is before the maid of honor, hype up the crowd, "Are you ready for the greatest wedding speech ever?! I can't hear you!!! Are you ready for the greatest wedding speech ever?!?!", once they yell back like Hulkamaniacs, drop the, "Well, that's after mine to the maid of honor."
Would've tried it had my speech not been last.