Start early.　

Start developing your talk sooner not later. The more time you have to prepare, the more confident you"ll be.

Research your audience.
Find out everything you can about WHO you will be speaking to. What do your audience members have in common? What are the challenges they face? What is their education? The more answers you have to questions like these, the more you"ll be able create a speech that they'll want to hear.  
 
Don't worry about being original.
If you speak passionately, from your heart, and believe what you say, it doesn't matter if you're the first person or 15th to speak about your particular subject. The originality you provide is your voice and your passion.  
 
 Keep it simple.
Smaller, shorter chunks of information are easier for audiences to absorb.  
 
 Make them an offer.
Offer your audience a solution to a problem, a challenge to how they think or act, or an opportunity to learn something new. Create your speech around that offer ("Today I'm going to give you 3 tools to eliminate procrastination from your life forever...").

Create a conversation.
Instead of creating a "speech," develop your talk as a conversation between you and the audience. 
 
Involve the audience.
To create that sense of conversation, interact with your audience. Ask them questions ("How many of you would agree with that?"). Give them things to do ("I want you to write this next fact down...").

Listen to yourself.
How your speech sounds is much more important than how it reads. Create your speech for the ear, not the eye.  
 
Rehearse. Revise. Repeat.
Practice your speech as much as possible; revise it continuously so that it"s just the perfect speech for YOU to deliver.  
 
Have fun!
Keep the process of creating your speech simple and light. If you make the process fun, your speech will reflect that and you will deliver a super speech!