The short answer? Do something meaningful. Speakers at any conference, be it TC Disrupt or All Things D or CES or the DNC are one of the main attractions. People within the community want to see or hear from those who are having an impact. So if your question is - How can I sell myself as a speaker before I've achieved anything of note other than founding a startup? You can't, you are not who the organizers are looking for as a draw to the conference nor are you who the attendees are eager to see/hear.