10: Always refer to your owner's manual for the maintenance schedule and correct products to use. Never stray from the recommendations, engineers make them for a reason.
9: Always dispose of fluids properly. Most automotive parts stores and some repair facilities will take old fluids for free.
8: Coolant is highly toxic, always keep children and animals away from it. Consuming it can be fatal.
7: Always tighten nuts and bolts to their recommended torque specifications. Over-tightening a bolt can be just as catastrophic as under-tightening one.
6: The brand of the oil filter does matter. Find the one with the best flow rate, which is typically Fram Extra Guard or K&N.
5: Don't attempt to maintain your own vehicle unless you are confident that you can complete it successfully.
4: You CAN mix standard and synthetic oil at any ratio without any issue. You can also switch from synthetic to standard and back to synthetic as you please without issues. This is an old myth that came about many years ago.
3: Never open your radiator cap or coolant expansion tank (overflow tank) when the engine is hot. You will get scalded, badly.
2: Double--check that there are no leaks in the system you just serviced prior to driving anywhere.
1: If you are jacking up a car for service, never just jack up one side, never use a spare tire jack to hold the car, always secure the vehicle with jack stands and never allow the floor jack to support the vehicle's weight.
Honorable mention:
Most 2000 and up cars do not have a distributor or a distributor cap, so a tune up involves just spark plugs and wires, in some cases. Even wires are being phased out in favor of coil-on-plug ignition systems.
If you are working on a cooling system, buy the 50-50 premixed coolant instead of full-strength coolant, it makes life a lot easier.
Buy the correct spark plugs for your vehicle. Running "hotter" plugs or premium plugs will not increase a modern, computer-controlled car's performance. Actually, it can decrease its performance, as the computer will compensate for the hotter plug. Also, never buy a plug of lower quality.
