On the night:

Before you begin, take two or three deep breaths.
Have a glass of water ready, and within easy reach.
Adjust the volume of your voice to the venue, and ensure the back row can hear you.
Open with something special - "In the last half an hour, five hundred thousand beers have been consumed in Cape Town ..."
Open with your hands together.
Keep your hands above your elbows.
Remember to smile.
Stand with your feet slightly apart and knees loose.
Accept that you will be nervous - everyone is nervous on their special day.
Remember your guests want you to give a successful speech.
Respond positively - and with a smile - to hecklers.
Finish the speech before the guests expect.
Close on a high note - "Lastly, I'd like to thank Helen Zille for ensuring that the bar bill is going to be less than it could have been!"

Be aware :

Don’t drink more than the minimum beforehand.
Don’t try to memorise your speech.
Don’t start until your guests have settled.
Don’t mumble.
Don't say "You know".
Don’t speak in a monotone.
Don’t look at your watch.
Don’t rush it. You have rehearsed, so keep to that speed.
Don’t repeat yourself.
Don’t fidget.
Don’t put your hands on your hips or in your pockets.
Don’t make jokes that will only be understood by a minority of the guests.
Don’t stray too far from your script (or cue cards).
Don't lose your temper for any reason.
Avoid sounding opinionated.
Avoid bad taste.
Avoid cliches.
Avoid jokes if you are not good at them.
Avoid dirty jokes unless you know everyone will enjoy them.

Before the wedding :

Rehearse your speech again, again and again.
Rehearse in front of a mirror.
Practise varying the pitch and volume of your voice.
Build natural pauses into your speech.
Check the speech area in advance.
Check the microphone.
Check that the water is in place.
Organise your script or cue cards so the you can see it / them easily.
Visualise yourself delivering a loud, confident clear speech.
Go to the bathroom before you start.