I always inspect all fuses for rating, still good and fuse clip strength and tarnish.
I inspect the coils visually and by manually activating them to make sure they have free movement. A burned coil is a clue that some board work may be needed. I also tug on the coil diodes while I am there.
I then inspect the boards looking for burned components (the lamp resistors are usually toasty but not necessarily bad). I tug on the socketed chips by hand. If 1 comes out that socket needs to be replaced.

When you turn the machine on listen for activated coils (ignore the coin reject coil in the door). Turn off immediately if a coil locks on or you smell burning or hear buzzing.