How can you successfully negotiate a speaker's availability and schedule?

In case of high in demand speakers, I would ask for their agenda for the following year, and request my admin staff to prepare at least three dates to choose from that our organisation would love to have them speak for us. On receiving written approval, our team would carry on finalising other matters like: payment for speaking, accommodation and airport transfer costs, if applicable, and any other logistics of the event. In case of newbie speakers, there is more flexibility in return for the exposure to a wider audience. Depending on the schedule available, there is a chance of getting a few events across the year at a reduced cost in return for exclusivity. It is always better to work on a win-win scenario.

You cannot and should not pay speakers. Provide them with complimentary services like a room where they can stay and sleep during the conference, VIP area with more food, invitation to private dining events, gift at the end of their session.

Check if there are videos of their previous talks on YouTube and other platforms. Also compare their topic and reasearch with other speakers from other countries, their personal contribution may be relevant in their national context

Previously my speaker budgets were very few and far between. So I heavily relied on my messaging and building a relationship with that person and explaining the goals of the conference and exactly what was needed from them and where possible taking the pressure off them.

If possible, offer perks such as travel arrangements, accommodation, or additional exposure to make it more appealing for the speaker to adjust their schedule.

Accommodation is almost mandatory for speakers from other countries and living far from the hosting city. Refunding the flight is a bad choice, sometimes some organizer may provide a forfeit amount for covering a part of it. Of course exposure and recognition are ever attractive for speakers looking for a conference where they can share their personal experience and research

Approach the negotiation with respect and understanding. Acknowledge the speaker's commitments and demonstrate a willingness to find a mutually beneficial solution

Important: ask updates about their presentation, availability, and flight to avoid last minute "no show" and issues. Asking for a copy of the presentation the day before the event is a good and polite way to confirm that everything is ok and the speaker is ready.