Prevent stuck wheels:
Apply a [very] thin coating of anti-seize to the mating surface of alloy wheels to prevent them from fusing to the hubs.
Anti-seize your lug bolts too (of course).

Reduce 'need to bleed':
If you need to disconnect a brake line, you can prevent excess fluid loss (and the need to bleed air from the entire system) by wedging the brake pedal down first. I have a broken ax handle that is just the right length for this. You can even use the power seats to adjust the pressure.

Baste and cut
Cut your brake-bleeding load by sucking out the reservoir with a turkey baster first. Suck it out, then fill with fresh fluid. Less bleeding will be required. Do not use baster for cooking again, just to be safe!

Protect your bleeders:
Are the rubber caps for your brake bleeders missing or torn?
That's trouble waiting to happen.
Cover them with some foil tape (hardware stores), or a glob of silicone gasket maker (just sitting on the tip, do not pack it in).
Silicone gasket material can be easily plucked off the next time you need to bleed.

Protect your bleeders (2):
Place silicone grease on brake bleeder threads to prevent seizing. This is a thick grease available in many auto parts stores [NOT silicone spray!] Material will not harm system (like petroleum greases or oils would), and bleeding will flush out any excess.

Marvelous Milk Crate
An overturned milk crate appears to be the ideal work surface for driveway mechanics doing work on a brake caliper, such as pad replacement. Just the right height and size so that the caliper does not dangle from the hose.

Harness The Power of Hydraulics:
Need to move a big fastener on your undercarraige?
Place your floor jack under a breaker bar handle, and lift!
Much better than messing with pipe extensions, safer, and takes less 'swing' room. Capable of providing precise and massive torque for crank pulley bolts and such.

Winter Warmth:
This may be obvious, but many jobs can be made more enjoyable in the winter if you warm the engine first. A warm engine can even make front suspension or front brake work more comfortable. That motor is a big radiator!

Exhausting:
Want to locate an exhaust leak fast? When the car is cold, have an assistant place a gloved hand over the tailpipe. The leak will become much more pronounced for easy location. If the car stalls, or your friend's hand cannot hold back the pressure, there probably is no leak, or not much of one.

Less Exhausting:
Those big MB exhaust pieces can be super heavy and awkward to position, particularly for a driveway mechanic. Balance the exhaust on a rolling floor jack, then roll it under the car and raise it into position. No problem man!

Shrinkage:
Does everyone know about the wonders of heat-shrink tubing?
Electrical tape sucks. It deteriorates into a sticky mess within a few years in wet or hot conditions. A soldered splice covered with heat-shrink is forever. You can even heat-shrink over crimp connectors to keep them dry. Heat shrink tubing is easy to remove with a knife if the connectors need to be pulled apart.

Liquid Electrical Tape:
Formerly obscure, but now easy to find, liquid 'electrical tape' is far superior to actual electrical tape. This stuff is great for sealing where wires enter a multi-pin connector, the ground you just cleaned, or any exposed copper wire strands that could wick up moisture.

Anti-seize your lightbulbs?:
That's right. Ever had corrosion on your brake/turn/running lightbulb bases or sockets? I'm sure any grease would do the job, but those anti-seize folks have the handy brush, so that's what I grab. Warning: Do not get grease anywhere near a halogen bulb!

Urethane Sealants:
Moisture cure 1-part urethane sealants are a modern marvel. They are super sticky, super strong, super elastic, and long-lasting. These are ideal for sealing up holes in your body. Unlike silicones, these can be top coated, and I think they form a much stronger bond. Do not get any on your skin, as the moisture in your skin will cure it instantly. I have found that PL (Pro-line) Polyurethane Roof and Flashing sealant (readily available at major home centers) is the right consistency for auto use, and performs as well as any of the more expensive products from Bostich, 3M, etc. It does cure somewhat slower than the others, but this can be an advantage in humid weather. I find the 'window and door' urethane sealants are thicker, less elastic, and not ideal for auto use. I have had several samples of various brands on a very exposed piece of sheet metal up on my roof for over 5 years, with no signs of deterioration.

Lube your seat:
MB power seat components are very expensive. Lubing the tracks and other moving parts under there can prevent big trouble down the road. I use spray lithium grease for this. Use a paper towel or a plastic bag as a shield to prevent overspray. If any seat motion is slow or sounds 'strained', get right on it.

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1986 300E 5-Speed 240k mi.