Shoot the A and B standups to open the ball save gate, then fill as many squares as possible, ideally three in a row of the same “X” or “O” kind. With three in a row, shoot the saucers.
OXO shares its playfield design with Gulf Stream / Tropic Fun, but has a different rule set, so I’m listing it separately. Each of the six top lanes, two side lanes, two return lanes, center target and lower center rollover scores the tic-tac-toe square indicated on the playfield by that lane, placing an “X” or and “O” in it. For the top six lanes, you get the letter as marked - - 3 X lanes, 3 O lanes. For sides lanes, return lanes, center target and center rollover, you get whichever X/O letter is indicated as active at that time in the lit circle above the flippers. The top 6 lanes are “hard-coded,” while the other squares toggle. If you get three X’s or O’s in a row, that lights the side saucers for 5000. One of the first things to do is shoot up top to get the A and B standup targets; scoring both lights the center bumper and opens the gate at the right outlane. Your bonus is 1000 per lit square, so you want to score as many different lanes as possible. Ideally, you want to line up X’s or O’s, but do get squares whenever you can. I believe it’s that lower rollover that toggles the X and O. Bonus is tripled on the last ball, making the game rather last-ball-heavy. Key feeds: the kickouts from the two saucers. If you can hold the flipper up, live catch, or dead bounce to get the ball to a cradle on either flipper when the ball kicks out, and thereby set up a repeat saucer shot, you’ll clean up.