Anti-Seize
I hope I'm preaching to the converted. Anti-seize is $5 insurance against hundreds or thousands of dollars of future repairs. Almost any repair assembly should get extensive use of anti-seize because some day, you're going to have to repeat that repair.
There are 3 basic types of anti-seize. Most contain high percentages of aluminum, copper and/or graphite in a paste lubricant. A 2nd version contains higher copper concentration which allows use at higher temperatures and and increases electrical conductivity for use in electrical applications like O² sensors, spark plugs and ground strap connections. The 3rd adds nickel to provide greater anti-rust protection in very high temp applications like exhaust systems.
Anti-seize should be used on threads or nuts in most reassembly applications. And I'm dead-serious, MOST. If you have ever had a bolt or nut round off, a stud come out (instead of the nut), or had some close-fitting assembly refuse to come apart, then you are looking at an application where anti-seize probably should have been used. There are some applications were anti-seize should not be used, but if in doubt, it probably should have been!
Exceptions: Stainless steel hardware probably is not necessary. That it doesn't rust or oxidize is usually sufficient protection. If mixed, however, use anti-seize. For example a stainless nut going onto a steel stud or bolt. This does not apply to aluminum, where a steel bolt is going into an aluminum housing, such as the VW case. Aluminum tends to oxidize and creates an electrolysis reaction with steel, so the anti-seize provides protection from that fusing or galling.
Another might be specific lock-nut or lock-bolt uses, especially if they are using a plastic or chemical compound to achieve the lock such as Nylok nuts or the lock bolts (as in many disc brakes) that have a nylon insert or compound.
Anti-seize can be purchased in cans (usually with brushes in the lid), tubes and even spray cans. A $5 can will last for years of heavy shop use.
Some common applications you've probably experienced might include axle nuts. Remember trying to get off a nut installed with 250 ft-lb. torque and it wouldn't budge with a 500 ft-lb. impact wrench? Should have had anti-seize! A mini-version is the lug nut. How often have you found the lug nut you put on with a 94 ft-lb. (Bay Window) or a 123 ft-lb. torque wrench (Vanagon) that won't come off with an impact wrench or 2' cheater bar? Rotors are usually attached to the hub with a countersunk set screw, which the high temps of the rotor will fuse together. How about CV joints, where you're are trying to remove a socket-head screw buried deep into a trailing arm box? I think exhaust system hardware is a no-brainer. I'll even advocate loosening and reapplying anti-seize every now & then. How about the flanges on the cooling system plumbing? A Vanagon waterpump is bear enough to change without adding stripped out socket head flange bolts. Any suspension & drive-line component is a candidate, including bushings & ball joints. The flanges of my pick-up front rotors are so closely machined that they rust together and you can ruin the bearing hubs getting them off. Dodge doesn't believe in using anti-seize on the assembly line so the first time you have to replace the U-joints (They don't believe in packing them with grease, either.), the hub will be fused to the steering knuckle.
On the subject, but not a true anti-seize, are hose connections. Use of a grease anti-seize may contaminate the fluid carried. For most hose applications, I'll use a spray silicone, which usually helps protect the hose as well.
Anti-seize should NOT be confused or used with an "assembly lube", but that's for a future post.