I have, in the past several years, accumulated a cadre of tools and materials that I consider essential to maintaining and repairing model electric trains. They are:

1.  Repair manual for postwar Lionel electric trains (Greenberg and K-line are two distributors)
2.  Pencil tipped soldering iron (typical soldering station is around 50 watts but develop 700-800 degrees tip temperature) 1/16 inch diameter solder for electrical circuits.
3.  Soft towel or piece of plush carpet to cushion the cars and engines as you work on them. Some people have made a U-shaped padded enclosure to hold locomotives upside down while working on the wheels or pickups.
4.  Small phillips head screwdriver
5.  Small flat blade screwdriver
6.  Split-end screwdriver (for holding and starting small machine screws in those hard to get at places)
7.  Small needle-nosed pliers
8.  Small wire cutters
9.  Wire stripper (again for small wire)
10. Spray wax for shining/cleaning plastic bodies.
11. Nut driver set (1/4 inch and up)
12. Soft cotton cloth for buffing plastic surfaces
13. Small vise grips (6 inch)
14. Small center punch or nail set (drive out axles and set rivets)
15. Small hammer (8 ounce ball peen is nice)
16. Outside pliers for spreading loco frames
17. Electric drill with various bits
18. Multi-meter for voltage and continuity checks
19. Test transformer (6-20 volts AC) with whistle control and test leads with alligator clips
20. Stainless steel locking straight hemostats
21. Lionel "E" unit tool (ST-303)
22. Mild soap (Ivory is good for plastic shell cleaning)
23. Several soft nylon toothbrushes (for cleaning and also applying WD 40)
24. Small stiff wire brush (brass is best)
25. Ink eraser (pencil style) to buff armatures and contacts
26. Light weight machine oil and needle applicator
27. Light weight grease for gears and armature shafts (Lubriplate 630-AA)
28. WD 40 for cleaning metal and black painted shells, boilers, frames, and chassis)
29. Tuner cleaner (safe for plastics) for degreasing axles, iron core plungers, roller pickups.
30. Wire for roller pickups (Belden #8890 black stranded rubber coated)
31. Small channel lock pliers (6 inch)
32. Small bench vise with at least 4 inch jaws
33. Bench grinder with 6 inch fine wire wheel and one fine grinding wheel
34. Heat shrink tubing (several sizes to insulate spliced wires)

General notes on your work area:

Good lighting is a must!!! Plenty of light right on the job will save you frustration because you can see what you're doing and also what might be wrong inside the unit under repair. A strong surface such as a work bench or sturdy table is important. A card table is too flimsy except for occasional projects. The correct height chair if you like to sit or a high table if you prefer to stand is important for comfort and no stress on the back. Many repair jobs take several hours of concentrated effort and you don't want to get tired halfway through.

Good ventilation. There are times when soldering will produce noxious fumes that may irritate your eyes or nose.

Have a pencil and paper handy to make sketches of wiring or the way something goes together. You may not get around to finishing the job right away and the memory can't always be trusted. Also make a list of repair parts you need as you proceed.

Find a source of repair parts and a knowledgeable person who can advise you when things get tough and you need a part to get that locomotive back on line. There are many good reproduction parts available to replace worn or lost original pieces. Don't use the wrong screw even temporarily because it may ruin the threads for future use of the correct part.

Have access to a small child with eagle eyes to find those teeny parts that always fall on the floor at the wrong time.

There are, undoubtedly, specialized tools I have omitted or something you consider indispensable. However, I can safely state, if you have all of the above tools and materials, you can maintain and repair most of your engines, cars, and accessories.