Speaking in public ranks as the number one fear for most people.
But it doesn't have to be like that if you're prepared to put in some effort and follow some simple guidelines.

1. Accept you can't wing it
No professional speaker would give any kind of speech without preparing it.
And the ones that seem the most spontaneous are those the speaker has spent time, thought and energy on preparing.
Think about comedians.
Their routines are honed till they know in which places the audience will react well.
The jokes that don't receive any response are chopped out of the routine.
So understand you need to prepare.

2. Create an outline
Giving a wedding speech? Then you know the elements people include; thanks, anecdote, graceful praise to the bride.
All effective and memorable speeches have a structure.
Think of the occasion, think of your audience and work out what they need to hear.
What will make them go away thinking your speech met their needs.
Take the time you have for your speech and divide it into the elements you want to include.
Allocate a time to each and then work out what you want to say in the time.

3. Be concise
Rambling is one of the worst nightmares for a speaker and the most boring for an audience.
If they're kind, they feel embarrassed for you.
If they aren't kind they'll be hostile.
Your outline helps to keep you on track.
When you've made your points at any stage of your speech, stop.
Your audience won't thank you for talking down to them.

4. Be careful using humour
Leave the jokes to the comedians.
If you forget the punch line it's embarrassing and unless you know your audience well then you run the risk of offending someone.
Comedians are paid to take that risk, you aren't.
You can try funny, real stories, preferably about your own shortcomings or situations.
But be sparing until you're confident doing it.

5. Practise
This goes back to not winging it but you need to practise in a particular way.
Take your outline.
Then take what you have written for each part.
Now read it out loud at a normal speaking pace.
Time each section.
If you're new to speaking it will surprise you how long it might take.
Record your practice if you can because it will help you work out where you need to include more or take out some of your speech.
Allow for your nerves in your timing.
Nervous speakers often speed up until they are impossible to listen to.
All speakers get nervous before speaking.
The difference between professional and occasional speakers is that the professionals know how to use their nerves to power their speeches.

6. Avoid the number one mistake of reading your speech
There's nothing more boring for an audience than a speaker who has their head down mumbling as they read their speech.
Practising your speech will help you be familiar with it.
Avoid learning it off by heart because unless you're very good at that, it will come over as stilted.
Instead commit the main elements of your speech to memory so that if the worst happened and you lost your notes you could still make your essential points.

Wherever you give a speech or talk, be genuine.
Audiences will forgive speakers many faults if they feel a connection.
One of the best speeches I heard was from a business woman speaking about the struggles she had taking over a business.
She was so passionate about what she did and the people she served that the energy in the room was tremendous and she outperformed the professional coach who'd spoken before her.
What's most important when speaking is to care about the topic of your talk.