Simply use a classes .btn .btn-default and quickly create a general button.
Simply use a class .btn-roundedand quickly create a rounded button.
Simply use a classes .btn-lg .btn-sm .btn-xs and quickly create a different size buttons.
Simply use a class .btn-block and quickly create a full size button.
Use a class .btn-group-vertical
Use a class .dropdown-toggle and also add data-toggle="dropdown"