Definitely don't have a go at the in laws, not a good idea to have the families at war on day 1
Practise out loud, especially any jokes, public speaking is different to telling jokes, got to get the timing right
Funny stories about the groom is best , but nothing he will hate you for ( had a mate get married whose best man was on strict orders not to mention his college nickname of The Caretaker, as he'd serviced so many old boilers )