Updated: Sep 23, 2018
Let's face it, the bride might spend months agonising over her dress or which cover version of Hallelujah to play, but at the end of the day speeches can make or break a wedding, so take time to plan and do some research, as winging it rarely work. Nobody likes hearing "I didn't really prepare anything" unless you're Stephen Fry.
Aside from a simple toast, five minutes is probably the minimum time you should be going for. Make a list of the subjects you want to cover, then extend it into a flowing speech and time it. Don't mention your subject's university entrance rank or if they won a gold medal at the state swimming trials - this is not a CV.
Go easy on the tales of debauchery, too - this is not a 21st. And remember to involve the groom (or if you're making a speech about him, involve the bride), and make sure you praise them as a couple as well as individually. If you knew, find out about the time they met, it's great for your guests to hear a retelling of the meeting story. You'll want some jokes and good anecdotes in there (there are a million wedding-related one-liners available, just check Google) but as there will be a wide range of ages and disparate groups of people listening, keep it clean.
Never, ever mention ex-partners, Instead, do your best to make the subject of your speech sound funny, clever and kind; if you succeed, this is exactly what people will think of you.