Nearly every high-profile speaker has a website outlining their process, fees, and requirements for speaking engagements. They also have instructions on how to contact and book them.

I assume that you know basic details for target speakers such as what topics they have been speaking on, in what kind of conferences, and where they have been often travelling. Share your conference details for
(a) the kind of audience you expect
(b) the conference topics (multiple tracks if you have)
(c) the names of other confirmed speakers
(d) whatever program if finalized even if without the actual schedule
(e) the business and networking opportunities

Share the buzz and how the community is active and involved in your conference. This gives them a real behind-the-scenes picture your planning and vision of the conference.

Next, pick some of their tweets or blog posts (or their comments, notes) that talk about their related experience and skills, and write a note on how they can add real value to the conference.
Last, offer them some incentive to travel to your city, some travel points, a note on foods, culture or festivals. Most of the speakers who travel, love exploring the local places. Do not forget to talk about the hotel and basic facilities too.

Need more details? Setup a call and I can share more directions! :)

If you're looking for the best, that means you have a budget for hiring them. GREAT!

1) A site I recommend you visit is eSpeaker.com

2) You can also search for a company local to you (or not) that represent speakers. They'll provide you with the names and information of the best people for your situation.

3) Ask your audience for recommendations

4) Search using LinkedIn

5) Search using Clarity.fm!

This is easy. I do something similar all the time. Get on their mailing lists and respond to the auto-responders with the question. You will be surprised to find that many times you will get a reply.
Don't stop taking massive action.
Best of Luck,
Michael T. Irvin
michaelirvin.net
My books are available exclusively through Amazon Books. Check out my book "Copywriting Blackbook of Secrets"
Copywriting, Startups, Internet Entrepreneur, Online Marketing, Making Money

The easy answer is to give them something that they want. Although this could be money, it could also be access to your audience. Find out what they are interested in achieving with their speaking engagements, and then make that available to them.

Are they a spokesperson for cancer research? Agree to donate a portion of your conference fees to cancer research. You get the idea - find something they are passionate about, and help them.

To recruit high profile people to speak at a conference keep the following things in mind:
1. KNOW WHO YOU’RE TALKING TO
Whilst this might seem obvious, you will need to do a little research to make sure that the potential candidate you are speaking to could be a good fit for a position within your company. After all, you do not want to waste time discussing a position that has nothing to do with the candidate’s skill set. If you can, suss out the workshops or sessions your potential candidate may have attended or might be going along to later in the conference.
2. START WITH SMALL TALK
Engage your prospective candidate in a conversation relating to the conference or workshop topics. You do not want to invest your time and effort in a person who does not actually match your ideal candidate profile. These moments are the first of many conversations that may lead to formal interviews later down the line.
3. GET SUFFICIENT BACKGROUND INFORMATION
If the person you have met could be a potential fit for your team, find out a little bit more about where the person currently works and his or her responsibilities. If you know the person’s job title, you can more easily gauge if he or she might be looking to make a move.
4. MENTION A POSITION
Despite what I have suggested earlier, do not spend too much time making small talk unless you are genuinely interested in what the person has to say. If the person asks questions or displays body language that signifies interest, continue to elaborate on the opportunity.
5. FOLLOW UP
That way you can provide additional information on the opportunity and explain why you believe he or she should consider your offer. Some candidates may only give you their work contact information, particularly if they have just met you. If the conversation progresses naturally, they will be more likely to give their personal contact information at the end of the discussion. Next time you’re at an industry event, establishing common interests, evaluating potential fit and following up with them will help you improve your scouting efforts and attract suitable candidates who may not even realise they’re speaking to their potential future employer as you chat over a coffee during a session break.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath