Watch Paul's awesome home video series, "Kite Fishing Encyclopedia." Skip to 4:50 for the off-angle flying.
The trick is attaching a little asymmetrical drag or weight on one side. a combination of both, as explained in part 3, minute 12 below, is the best (that's where the gallery above is from)
And Check out the auto-adjusting bridling on the Flexiwing, at minute 11, and the weight system of tacking used on it:
continued. Tacking techniques again at 10:50: