Why a one sheet?  Do you really need one?  Is it required?
These are the questions I hear when I talk about a speaker one sheet.
I believe that as a speaker you need a one page document to share with event planners — it can be a pdf you attach to an email or a page on your website.  Either one works.

Elements of a one sheet. 
Remember first and foremost, the one sheet is about what you bring to the audience.

Picture of you — the real you.  Now, I'm not saying that you roll out of bed and snap a pic.  We still want to put effort into the photo, but let it showcase you and your personality. 

About you – the biography section. This is where you showcase your skills.  Show the event planner why you are the person to help her audience. 

Topic or topics  – showcase your signature message or messages.  Keep the focus on the audience and the problem your message solves.

Social proof – combination of testimonials from people who can speak to your skills and information on notable places you've spoken.  Do not worry, if you don't have much experience, that just mean you have to be more creative  (not deceptive).  Have you led Bible study?  Ask one of the attendees for a review.   Have you presented in a business setting?  Ask for a statement.

Contact information –  seems obvious, but I do like to state the obvious. 

Your one sheet is your foot in the door — create it to showcase how you can serve the audience and you'll get noticed.