How do startup board seats work?

Most jurisdictions allow corporations wide latitude to structure their management as they see fit. You can create the corporate entity and, through drafting the state filing papers (e.g., Articles of Incorporation) and ByLaws, identify yourself as CEO (or President) and board member, with the ByLaws or shareholder agreement identifying voting rights. Your interest in "keeping control" may be adverse to other founders or potential investors, of course, so the decision making of which you are referring is likely something that should be made multilaterally. Are you fronting most of the initial capital? Is the IP yours? Generally, your company charter (e.g., the ByLaws) is where boards, officers, voting, and other matters are detailed. "How" that will happen will depend on particular facts concerning your enterprise which are best left for a private conversation with local counsel.