What's the optimal way to pump gas?

Question for the engineers or the engineering-inclined. What’s the optimal way to pump gas? I’ve heard that waiting until the tank is almost empty can be bad for the engine. Is that so? Is it best to always fill it up, then refill it when it’s half-way through? Three quarters? Is it best not to fill it all?

I always fill it up, and then refill when the light goes on warning about low fuel, ‘cause it’s the most time-efficient way. How do you do it?