i used a similar method to the above..
keeping all the biggest numbers on the bottom row.. and the biggest number always in the bottom left corner and adding towards that..
so if you have a 1024 tile in the bottom left.. the next along will aim to be a 512.. then aim to build another 512 next to that by building 2 256's it really helps keep free space to keep it sequential like that..
and then never pressing the up key.. press the up key even once and its game over pretty much. (though i did use it right at the end)
in my system it also helps majorly to keep the bottom row full at ALL times.. this helps keep the big number in the bottom left..
its especially tricky to get rid of a number when you've got say a 512 or 1024 tile in there as it uses up a valuable free space from the rest of the board And it makes the row above essentially become your 'bottom adding row' losing you even more space.
and if all that made any sense...