Most people learn to do intarsia from a booklet, a tutorial, or failing that, a published pattern.
I learned by designing an intarsia-heavy project from scratch.
Fortunately, I then felted the heck out of the sucker, which hides almost any mistake.
Here's the backstory: No, I'm not Navajo. I don't live in the American Southwest. I don't have anything in the way of Southwestern decor or clothing.
Last year, I participated in a volunteer trip to the Navajo Reservation, where we spent a week on home repair for a few of the locals. One day over lunch I met a lady who helps run a local charity. She saw my recently completed Reasonably Hip, and the next day she invited me to her office to see some fiber-related crafts that she and the ladies of her family had made.
She showed me a rug, a hat, a crocheted purse, and a few pictures of the Navajo wedding basket motif. Each had variations on color and structure, but all of them followed the stair-step pattern with a gap on one side. "That's to let the evil spirits out," she explained. "If you're superstitious." (After designing this pattern, I've come to the conclusion that the women who originally created those baskets just told people that to hide the jog in the spiral. But then I'm a cynical knitter.)
See the gap on the backside? It's always supposed to go on the eastern side of the piece, or failing that, away from the vital opening.
She requested a couple Reasonably Hip-style hats with that motif. Whoopsies, I still haven't done anything about those, but I did happen to use the half-pound of Brown Sheep yarn I bought while I was out there (wonderful thing, expandable luggage) to create this purse. At Sunday's fundraising luncheon for the 2008 volunteer trip, it brought in about $20.
I plan to post a pattern for it ASAP, for any who are interested.