When I was teaching magic I liked to sit down with the person and explain all the different card types, creature, artifact, instant, ect...
From there I would give a quick two line type description of each color. eg. Red = fire, chaos, and destruction. White = holyness, protection, life gain ect...
from this most people I taught could pick which color they liked the sounds of most and I'd build them a simple deck of that color, only creatures, sorceries, lands, and an artifact or two. I would play a similar deck of another color and play against them till they understand the basic mechanics of the combat and turn sequence while I explained things to them. This usually took 5 or 6 games. Also each game was a best of three and since I would usually win the first I'd often "throw" the second by making consistently bad plays and choices so that it would show the trainee that, A: it is possible to win when you start out, just tough, and B: to always watch for opponents errors and exploit them.
After a while like this I'd give them a few instants for their deck and let them get used to playing things on the opponents turn when they can such as bolting an attacking creature ect...
All this usually worked and since I haven't had a dropped out student I think I turns out good by giving the player some basic survival skills and knowledge of how card types interact.
hope this helps