I am assuming you mean alternating joints (offset 6 inches from previous row).

I would lay it out based on the size of the full tiles. The best way to do that is to first find the center of the room (both ways) and measure the length of the room, and determine the number of full 12' tiles, and most importantly what is the remainder. For instance, if it were 12' 3", which would be 6' 1 1/2 inches both ways from center but you don't want 1 1/2 pieces on the sides. So you move the middle tile 6 inches away from the center and you now have 7 1/2" on each side. But when you consider the adjacent offset row, you will be back to 1 1/2 inches pieces on the sides again. So the best you can do is split the diff, and move 4 1/2 inches. Laying loose tile on the floor is easiest way to confirm how they will fall. I don't know what the official minimum sized piece is recommended but I think 4" or so is pretty good. You have to look ahead even more if there are doorways or islands to contend with. Sometimes, you can't come out perfectly along every interruption, you may have to keep the larger pieces in the most visible and most walked on areas.

I would lay it out based on the size of the full tiles. The best way to do that is to first find the center of the room (both ways) and measure the length of the room, and determine the number of full 12' tiles, and most importantly what is the remainder. For instance, if it were 12' 3", which would be 6' 1 1/2 inches both ways from center but you don't want 1 1/2 pieces on the sides. So you move the middle tile 6 inches away from the center and you now have 7 1/2" on each side. But when you consider the adjacent offset row, you will be back to 1 1/2 inches pieces on the sides again. So the best you can do is split the diff, and move 4 1/2 inches. Laying loose tile on the floor is easiest way to confirm how they will fall. I don't know what the official minimum sized piece is recommended but I think 4" or so is pretty good. You have to look ahead even more if there are doorways or islands to contend with. Sometimes, you can't come out perfectly along every interruption, you may have to keep the larger pieces in the most visible and most walked on areas.