This is probably all you wanted to know. The symbols can be rotated and flipped around.

Schematic Symbols
Schematic Symbol Example Comments
intersection three segments of same wire If N things are wired together, then N-2 of them will have will have a double wire on a solder lug.

Picture a single file line of mountain climbers roped together. The guys in the middle have two rope segments on them, the guys at each end only one. Wiring in the bingo is like the rope.

Except for small jumper wires, a solder lug should never have two different colored wires attached to it.

Symbol shows four segments of the same wire and the wire ID. The intersection has a dot (which is sometimes so small you can hardly tell).
two different wires Both wires will have different ID's. Two unrelated wires that cross on the schematic.
invisible wire Wire pointers are used to avoid drawing a lot of lines (like 25 lines from the playfield hole switches to the search disc), really long lines that would have to cross a bunch of other lines, or when there's not enough room. A connection pointer to another wire somewhere else. Usually the label tells you the grid coordinates of where the rest of the wire is drawn on the schematic.
normally open switch normally open switch Normally open switch and label identifying where the switch is located.
normally closed switch normally closed switch Normally closed switch and label identifying where the switch is located.
spdt closed switch spdt closed switch SPDT switch and label.
tilt tilt Collective symbol representing the pendulum tilt mechanism and all the normally open slam tilt switches mounted inside the head and cabinet.
fuse fuse Fuse and rating.
transformer winding
transformer winding 		transformer winding Transformer winding and voltage it produces.
lamp
lamp
lamp 		lamp Lamp and function label.
resistor resistor Resistor, usually with value and wattage.

Pictures shows lower power cylindrical carbon resistor and higher power rectancular ceramic resistor.

motor
motor 		motor Motor and function label. Picture is one of the 6 or so styles of motors
adjust plug adjust plug Plug and function label. Some adjust plugs have double rows of pins like the plugs between the head and cabinet/playfield.
coil coil
plunger coil 		Coil and what unit/relay/thing it is part of. Picture shows two major styles of coils. The bottom coil shows the plunger also.
trip relay trip relay Trip relay and function. A trip relay symbol is a coil in a box with an integrated cutoff switch.
some kind of wiper some kind of wiper A wiper/contact plate and where it is located. Could be part of a stepper unit, or something like the mixers, spotting disc/wipers or search disc/wipers.

Any box with diagonal lines in it is a wiper/contact plate. If the box is really small, the diagonals lines might be left out.

There's probably a few more symbols on later model machines for diodes, transistors, and capacitors. I'll take a look and add them eventually.