How to minimize waste when installing the subfloor
There are no big secrets to be had here. You start with a full sheet, tongue just inside flush, and run a row, butts centered on your joists. You then use a "beater block" to drive the second row into the first, staggering butt joints at least one joist space (ideally roughly half the sheet's length). I like a 3-4' 2x4 that I can stand on and whack with a sledge hammer. If the cutoffs are long enough, start the next row with them. If not, they're scrap. 

If you expect to end up with a very narrow final row, consider ripping say 12" off the tongue edge of the first row to make the last row wider. While the t&amp;g joint eliminates most concern, rows of 10" or less are inherently weaker. Of course, you could also block under those narrow rows if you prefer.