Hi,
I need some advice on how and when to lube cars and engines.  And how to do it properly.

Thanks!

It all depends on how much you run your trains. I repair trains for a shop and I have seen both dry gears and over lubricated gears. Just recently I repaired a 30 year old European brand loco and  there was old dried grease caked on gear box wall's, but non on the gears themselves. I was surprised that the gears had not worn down although there were burs on the edge of a couple of gears which I removed with a sharp knife.   
In answer to your question I check my locos every year ( I don't run them very often also my collection is extreamly small, besides, I enjoy tinkering around with them.) As far as my freight car's go I lube the pinpoint axles with graphite and what a difference it makes. I use to use light oil in the journal box of the pinpoint axels, but over a period of time I found fluff / dust collected in this area.
As far as motors are concerned i only lubricate the bearings. To lubricate the bearings I use a heavy oil, I put a couple of drops on tin foil then using a sewing needle or common pin I dip the pointed end in the oil and transfer it over to the bearing. Run the motor for a few seconds and you are all done. It is important not to get oil on the carbon brushes, as this can lead to a burnt motor.
Hope this helps.
Robin.