dont buy a flower, turn down the drink, get picked at dons, find yuffie, give her a tranquilizer on the ship, go with her to the battle arena (Dynes scene)...
also, if you dont use tifa or aeris in your party and only talk to them if its needed to progress the game, then you'll get her as a date. cant really imagine that tho, just cause i havent tried it out yet :P