Here goes:

Take a deep breath and then, in as clear and confident a voice as you can muster, ask for the attention of the guests.

Before you launch into the toast and for the benefit of people who don't know you, briefly identify yourself and your relationship to the couple.

Start by saying something complimentary about the ceremony you have all just witnessed.

Making it up as you go along is not a good idea. Instead, well before the big day, write down any positive thoughts you have about the couple and the good things that other people have said about their match.

By all means take a walk down memory lane in your speech but choose a memory that involves both the bride and the groom.

Don't mention previous girlfriends, boyfriends, or spouses. Don't talk about the cost of the wedding or wedding gifts. Don't talk about future plans the couple may have confided to you. This includes pregnancy and children. And don't make jokes about the honeymoon.

Keep it warm, personal, and brief. If you are a stand-up comedian, insert jokes. If not,  play it straight. It's safer by far.

The Internet is awash with great quotations that you can plunder to start off your speech or from which to take inspiration.

Do end the wedding toast on a high and hopeful note. Express all the good wishes in the room for the new couple's happy, healthy, prosperous future.

Finally, ask the assembled group to join you in the wedding toast, lift your Champagne glass (which you have remembered to top up before the speech!), and say, "To (name of bride) and (name of groom)...."

A few tips to remember:

If the wedding toast is being recorded by a photographer or videographer, visit the bathroom before your moment in the spotlight to straighten your hair and clothing.

Keep the speech short. Focus on the couple, and face them when you toast. Avoid talking about your own marriage or relationship.

Keep in mind that older people and children will be present, so no blue jokes.

Allow yourself time beforehand to rehearse the speech. If you tend to get nervous in front of groups, it's okay to read it from a card. Just let your genuinely warm feelings for the couple shine through.

***Do not get drunk before you are due to stand up and give the speech.***

And do remember to smile!