Well, as I was taking my front wheels off to put on my race pads for a Super Lap event, I managed to snap off one of my lug bolts. It is not the end of the world, and not very hard to fix. The down side is you can't really race that day with only four lugs. The up front alibi is that I haven't done this for the rear wheels, so I don't know how the procedure is different.
1. If you need to drive the car, make sure the other four lugs are properly torqued. I wouldn't recommend this for long term, but it will get you to the autoparts store and back.
2. Once you are there, buy a 12mm x 1.5 lug bolt that is 45mm long. You will also need a open end 12 x 1.5 nut and a washer.
3. Chock the back tires, jack up the car, take off the tire.
4. Remove the two bolts that hold the brake assembly on the rotor. It is a 17mm socket. One on the top, and one on the bottom. They hold both the brake assembly and the dust shield(?), or whatever that plate is.
5. I pulled on the dust shield / plate, but it didn't want to come off. Rather than fuck with it, I just removed the entire brake caliper assembly. That gives you some room to get at the back side of the lug bolts. Don't let the brake assembly hang by the brake line - hang it up, or prop it up. I used my car wash bucket.
6. Turn the front wheel until the broken bolt lines up whith the access hole. Bang it through with a hammer. It only took me three shots. If you are having trouble, maybe some WD-40 is in order.
7. Reach in from behind to slide in the new bolt. Put a little lube on the washer and nut and thread them on the new lug. You will need to tighten it way down to pull the new bolt in and seat it properly. I have a long handle ratchet, which generated plenty of torque. You can also use an impact wrench if you have access to one.
8. Reattach the brake assembly, put the wheel back on, buy new lug nuts because one of them has the snapped off end of a bolt in it. You can use the open end nut as a temporary fix.