Preparing for Repairs and some good practices

You would need most of the tools that is recommend in the maintenance section. In addition you might require some specialized tools , that will be introduced for the specific repair job.  But before that , your best friend here will be the "Factory Repair / Service Manual".  For older cars you can buy a CHILTON or HAYNES Repair guide.

But I have noticed that these guides tend to be a bit generic across several model/engine types and may not be the best guide for a beginner.  If you can find a factory repair manual online or purchase it from a dealer , it would be very dear in your repair endeavors. Factory guides usually have elaborate pictures and part arrangement  and very detailed set of instructions including the torque specs. See the picture for an example of a factory guide :

Note : A lot of the self help here assumes that you have backup ride/car - Friends,room-mates,family etc.because you need that for running to the store to buy the part or for the trip to the dealer to get the fluid. Oil is drained off the engine and you start to put the filter, realize that is the wrong need a ride to change it out.

Good Repair Practices

1.) Antisieze compound  - Always use an antisieze lube around the thread of bolts before you tighten them. You can use on bolts that are exposed to high heat or corrosion like spark plugs for example.

2.) Penetrating Oil -  This fluid can be sprayed to free rusted nuts and bolts so that they can be removed, because it can penetrate into the narrow space between the threads of two parts.  Usually it can take a few hours for the Penetrating oil to take effect, so you may spray it early on. PB Blaster and its application as shown below is an example of how rusted nuts can be freed. WD-40 is a similar fluid , but can be used as a cleaner as well.

3.) Use a Torque Wrench - A wrench , mechanical or digital that will make sure you tighten the nut and bolts to required  torque specifications. Always use a torque wrench, if the  torque spec is accessible and the nut or bolt is easily accessible. Examples include - Spark Plugs and most bolts that go on the engine.

4.) Take a picture with a Digital Camera - For obvious reasons , before you take apart something it is a good idea to take a picture , that you can go back to if you have trouble figuring out the assembly.

5.) Never creep under a car supported by just a Jack. A Jack is only a lifting equipment and not intended for support. Always support the car by a Jack Stand or similar before creeping under.

6.) For Protection against chemicals use/wear protective nitrile gloves and for safety use  goggles as required.

7.) Always engage parking brake, disconnect battery and keep windows down during repair as needed.