Get things in order
The last thing you want are flimsy notes falling everywhere on stage or a projector, laptop or microphone that does not work. Do proper sound checks, have all batteries charged and keep a backup of your digital presentation material.

Do not fear rejection
Most fears when it comes to speaking in public are irrational. Your audience would not attend if they do not value what you have to say.

Mirror, mirror on the wall
Practice your speech in front of the mirror as if you were speaking directly to someone.

Pay attention to:

Your facial expressions
Your gestures
Your body movements
How welcoming you appear
When you have gentle expressions and a calm demeanor when you speak, you will be more welcoming to your audience.

Camera, lights, action
Record yourself. Take your cellphone or any other recording advice and record your entire presentation. You will hear from this recording what you sound like to an audience and where to improve.

Get a spectator
There are plenty of people you can practice on. Be sure to tell the person to be completely honest with you in their critique.

Examples of people you can practice on:

Your significant other
Your friends
Your parents
Your dog…

Speaking directly to another person will help relax you and give you experience with getting feedback from someone. If they have questions about your speech, it is likely that members of an audience will have the same questions.

Call on an expert
There are hordes of mentors and coaches out there. In addition you can also join clubs or groups like Toast Masters.

Hydrate
Drink a glass of room temperature water before you speak. This will lubricate your throat and prevent your mouth from becoming dry whilst you speak.

Imagine them naked
Ok not really. However do not overthink your audience reactions and facial expressions. There will always be a phone ringing, a crying baby or a yawning face.

Slow down
Avoid talking too fast. Taking too fast can interrupt your breathing patterns, this will increase anxiety and leave you feeling out of breath. Practice to speak slower this will make you much more relaxed.