@Ceili,
I found this problem the hard way: Up until recently I used these (microfiber) cloths I bought. However, when I dried the windows after cleaning, they streaked the glass. Whn I washed the cloths, I did so with my laundry (using drier sheets). I figured out (afterwards) that the drier sheets have softener and softener streaks the windows.
So if you dry windows with cloths, do not use anything that has fabric softener on them. Epsecially true in a hot climate. It streaks up surprisingly quickly.
Also make sure there is no wax residue on the cloths as that will streak the windows too.