i dont use any of the free daub stars unless my power ups are full (because you cant earn more powerups if its full. the game allows 3 to be held at a time) or until the very end. this is because the game can potentially call a number you use a free daub on, which means you could have used it elsewhere where the game wouldnt have called another number.

any x2 powerups should be used at the very end. you only have i think 5-10 seconds that the x2 points are active. the more bingos you have when you hit x2, the higher your score gets. this is how you get a 73,000 score.

the yellow powerups are to be used right away. this is because they increase your power up meeter and can give you more earned power ups in a game. take a quick look at your board, see where clusters are, hit that yellow and pick a number. i for one have found that the recommended larger bingo ball out of the group of 4 is the one you shouldnt choose.

this has worked for me at least. hope it makes sense and it helps!