Quoted from Otaku:

Preliminary: Make sure backglass is secured in the head.

#0: Remove the ball(s) from the machine and store them somewhere safe. Keeping them in place during transport damages the playfield, plastics, and targets. You can do this by popping them out of the trough by hand, of if it's a machine with one ball and you have the time, sometimes I power on the machine and start a game and just let the machine pop the ball out for me to grab in the shooter lane then I shut it back off. Whatever works for you. This obviously would not apply to multiball games.

#1: Fold down backbox and use a ratcheting strap hold in down to the body. If your machine is not the type that folds down (prior to the mid-80's or later for some), disconnect all backbox connectors that flow through the port hole from the body up into the head. You may want to label these if it is a solid state machine, but they are usually all keyed differently anyways. Not always.

#1.5 (If removing head): Remove head bolts one by one while having a partner or your other arm holding the backbox in place. I have found that most backboxes will simply not stand in place due to gravity. The bolts are needed to keep it upright, so if it is not held in place while the bolts are being removed or added, there is a good chance it will tip forward. When done, lift the backbox off of the machine and carefully set it on the ground. You may shrink wrap this if wanted. Leave the backglass in the machine unless the head is damaged and does not keep the glass secure. It is much safer to store the glass there for transport than anywhere else. Handtruck to vehicle. It is preferred to transport it in it's normal orientation, because if it is laid flat there is a much bigger chance of something falling on the wide backglass and damaging it, however it also will not tip over if laid flat. Use what works best for you, but be careful.

#2: Lift the back of the machine and put a stool under the back of it so the back legs are in the air. If you do not have a stool, you can use a friend or if you're alone I have even seen some people prop the machines up on their knee, however this takes quite a bit of effort. I have a stool or two dedicated to this that I keep around. With the back of the game lifted, begin to remove the back legs. Remember to keep the bolts in a safe place, and keep them together. With the back legs off, set the back of the machine on the ground by lifting it up again, sliding the stool out (if applicable), and carefully easing it to the ground slowly.

Your machine should now be at an intense downward angle with the head removed or folded, the back legs removed, and the front legs still in place.

#3: Carefully tip the machine up onto it's back (90 degree angle from normal set-up position) so your coin door is facing the ceiling/sky. This is the easiest part, remove the front legs with no lifting or trouble at all. Again, store bolts and legs together securely.

#4: Making sure all plugs are tucked nicely inside of the body of the machine, shrink wrap (if applicable, I find I don't do this more often that not but depending on condition of said machine you may want to, with cardboard around the long bottom edges to avoid damaging the wood), and handtruck to your vehicle. Slide the handtruck under the bottom part of the machine so your face is closest to the coin door, and so the machine is still in this "storage" position.

#5: With the pinball machine at your vehicle (van/truck/SUV), slide the machine off of the handtruck (should have little feet on the back of the machine to avoid scratching the back of it on the pavement) and wiggle it over so the glass is facing away from the tailgate. Give it enough room away from the tailgate so you can tip it at an angle. Tip it at this angle, so the bottom of the front of the machine is laying against the tailgate. Now lift and slide the body of the machine up and in (this is where your cardboard and shrink wrap come in handy), fully into the back of your vehicle. I have found in my own experience that using the side doors of a van (if you have one) with seats removed is a lot nicer, as you avoid the hatch latch and a large inner plastic piece.

#6: Secure the machine in the back of the vehicle, secure the head, and secure the legs so they don't do any damage to your machine or backglass/playfield glass.

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Unloading the machine is basically backwards.

Here's the quick version:

#1: Unload, slide back out and set the back of the machine on the ground, tilt upwards so it sits flat. Slide handtruck underneath.

#2: When in desired location, de-shrink wrap if added. Put the front legs back on. Tight, but not too tight or you'll strip out the plates inside. This is the most frustrating thing in the pinball hobby. Please do not strip them out, for your sake and for future buyers' sake. It is not fun to find out when you have the back of the machine lifted in the air.

#3: With the front legs on, tip machine to that intense angle again, where the front legs are on (and being rested on) and the back legs are off.

#4: This part is a bit more difficult than taking it down, as you're now much further down than before. You'll need to lift the machine up not only to it's normal resting position but a little bit above and slide your stool under. I have done this myself with a lot of strength and a crafty foot to slide the stool under when nobody else was around to help, but I would suggest having a friend or family member help you lift and/or slide the stool under for the sake of your back. With the back of the machine in the air once again, put on the back legs.

#5: Lift up, hold, slide the stool out, set down gently onto the back legs. Your pinball machine now should look normal, just missing the head.

#6: Unstrap your head, fold up into upright position, and latch/bolt.

OR

Make sure power cord is going through slit in the back of the machine before putting bolt-on head on. The second most frustrating thing is finding out you forgot to do this when you have already bolted the head on, as you cannot do this after.

With that done, lift the head onto the machine with a friend and have one of you hold it steady as one of you bolts it on. It can be a bit of a pain to find the holes (especially the first and second ones) but feel around to find them. You can even reach your hand in under the head to get a feeler of where they are. They're a pain to find for a reason, if they're not going in, your head isn't placed evenly upon the body. Obviously, the bolts need to go in straight, so adjust the head by sliding it very slowly on the body while somebody else supports it.

#7: Reconnect head plugs if needed. Check the rest of the plugs to make sure anything didn't come loose in transport.

#8: You may want to open up the playfield and check the back of the cabinet to vacuum out all the dirt and junk that may have slid to the back during when we tipped it back, especially metal pieces that cause shorts.

#9: Make sure the backglass is still secure, fuses are still in place and seated correctly and firmly, connectors are seated properly and firmly (again), reinstall the ball, and turn on your machine and enjoy!