A split board is one option, as pmaggie pointed out.
Another alternative is to get a board with a flat outline (i.e., little rocker), as these tend to get going in lighter wind than board with more rocker. Stiffness and a rectangular outline also helps. Finally, maximize the width, as the increased surface area will help you start planing earlier.
So, basically, unless you want a split board, you should be looking for a flat, stiff, rectangular board. In flat water, those can get going really early and will typically perform very well (they'll hold a solid edge and will generate tons of pop, particularly if they have thin rails). However, that type of board normally won't feel very good in choppy water and waves (though there are exceptions - the old Skywalker boards were pretty damn good in almost all conditions, and were excellent light-wind boards as well).