Write your reason for inviting them to be your "chief guest. " Tell them if they will be expected to speak to the group and if so, for how long.Based on our years of experience and some extra research, we came up with this stepbystep guide to writing stellar guest speaker invitations. Present your credentials, explain how your expertise aligns with the conference theme, and express your enthusiasm for contributing. Send sample invitation letter for guest speaker via email, link, or fax. You can also download it, export it or print it out. A sample invitation letter for a guest speaker to speak at an annual dinner. Your speaker or performer's invitation should be a formal letter or email, outlining the reasons why you're inviting them to your TEDx event. I hope this message finds you well. How to fill out the Sample Letter of Agreement for Speakers?