I suggest that you take the glass off, clean and wax the surface.
Clean the glass over the playfield and the glass on the back box.
Try to acquire a manual, assuming you didn't get one.
Check if any rubber needs replacement.
Check all light bulbs to see if any need replacement.
Verify all targets and rollovers work as they should and adjust as necessary (use a ball for the test).
Same thing in the back box, check light bulbs and such.
If the balls are rusty or worn out, get some new balls.
Have fun playing the machine.