A toast should happen early in the evening.
Even though this might not be your first priority, it is better to do it at the beginning of the evening.
One has the right to ask people to be silent. Asking your guest “Silence, please” will clearly make an impression, but remember to do it politely and avoid being aggressive.
One must always stand while making a toast.
Bring your glass to your chest. If you feel your arm going numb during your toast, this certainly means it is time to put an end to it. Remember your arm strength is your natural timer.
Keep your style sober, and avoid pompous phrases. All the « May your fellows respect you, troubles neglect you and angels visit you» may sound glorious in a Church, but out of context, it could sound rather ridiculous.
If your boss is in the same room, avoid making him cutting remarks, even if on the tone of humor.
Don’t ever use terms like “poke fun” in your toast.
When you don’t know what to say, simply rejoice with “Cheers to us, and forget about the others”. You will see it works each time.
In a word: be incisive.