Don't forget to check your balls.... You could start by putting on some Barry White and shout "Woman! Time to check...."
Seriously tho, make sure your balls are good and not rusty/pitted/nicked.... they'll wear a playfield fast....
Also, if it is a solid state machine and powered by regular batteries, change your batteries once a year. Once a year might be a bit too often but it is cheap insurance against battery damage. If it is a rechargable (nicad, etc) I'd keep an eye on it too. Especially if it is mounted on the system board.... I'd relocate it off the board.