The reason I say My Maintenance Tips is these are based on my observations as an operator and my repair experience. As of this time I have serviced over 750 engines. Some may disagree, but It's what works well for me.
Lubrication - Lubrication is important but in my experience many use far too much. I lubricate the gear box using a lithium based grease. Using a light hobby oil, I lubricate the oil wick in the rear of the brush bracket, the armature shaft at the thrust washers, the smoke gear stud, and each end of the drive axles. I feel nothing else needs lubrication. These areas only need to be lubricated occasionally unless you are operating the engine very frequently. Always remove excess oil. You should not see any surfaces looking oily. This only attracts unwanted particles that will do more harm than good. Excess oil around the brush bracket and armature will cause the accumulation of carbon dust from the normal wear of the brushes which will accumulate in the slots between the commutator plates that can lead to damage of the armature. It will also gum up the brushes so they cannot move freely in the brush tube, preventing the brushes from maintaining good contact with the armature. I do not recommend lubricating any other axles or linkage. If they are working properly it should not be necessary.
Lock your reverse unit - Unless you are performing operations where you need to run your engines in both directions lock the reverse unit in forward. Most times the contacts need to be replaced is from holes being warn in them. This can be minimized by locking the reverse unit. Occasional cleaning will still be necessary but the contacts will last longer. (Also, I do not lubricate the reverse unit except for a drop of light oil on the hinge point of the lever that turns the drum.)
Smoke units - Always use a funnel to fill the smoke unit. The smoke fluid will turn into a shellac like coating that is very sticky and will hamper moving parts like the smoke wheel gear and linkage.
Do not operate you engine without smoke fluid unless it has a switch to turn it off. A dry wick will be damaged by the heating element and the smoke output will be affected. You can tell if you wick is bad. When you first start the engine you have good output that tapers off after a short time, then you let it sit for a few minutes, and it works well initially on restart only to taper off again. The fluid cannot pass through the wick fast enough to keep a good stream of smoke going.
Keep all your wheels clean, including rolling stock. Overall performance will be better and you track will stay cleaner longer