Use Up Before First Charge
Battery technology has come a long way in the last several years. As mentioned previously, there is no longer a "memory effect" so you can charge/discharge to any level without negatively affecting battery performance.
However, there is a finite number of cycles in any lithium battery...and it counts as a cycle whether you charge a little bit or a all the way. To maximize battery life over the life of the device, you should deplete the battery as close to fully discharged every time to reduce the number of charging cycles.