The number and types of shares authorized in a start-up corporation’s initial Certificate of Incorporation is somewhat arbitrary. We generally suggest that a start-up initially authorize 10,000-10,000,000 shares of Common Stock (sometimes referred to in other countries as “ordinary shares” or “voting stock”). This amount of Common Stock enables sufficient shares for initial founder grants and for subsequent employee and consultant grants. In any event, should you wish to have a greater or lesser number of authorized shares in the future, such a change is easily affected through an amendment of the Certificate of Incorporation to increase the authorized shares of the class of stock that will be sold, if there are insufficient authorized shares.
All (or vast majority if you decide to use Founders Preferred Stock) of the initial shares should be Common Stock because future investors will demand preferred stock with rights and preferences superior to the Common Stock.