Best man once, my speech went like this
How we met
Childhood memory
Older childhood visits after wed moved away
Even though he's a kopite joke
Heartfelt story about him looking after me when I was working 18 hours straight on the reg
Him being a constant friend and never letting me down
But now he's met someone beautiful who somehow brought out even more of the best of him
His mum (rip) would be proud of who he is
Best wishes
Forgot to thank everyone, forgot to take talk about the bride, didn't crack any jokes really, ad libbed the lot, seemed to go down well
One thing I would say is there's a way to not let anything be left unsaid, without being too mushy. Be genuine and you'll be sound. If you try to be something you're not it will be much harder.
Good luck!