I've taught both of my boys to ride. In hindsight, I wish I had purchased a real balance bike and never let them ride a pedal bike with training wheels. Interestingly, my kids are very different and each required their own technique to learn how to ride.
1) For my first kid, I removed the training wheels and pedals, lowered the seat, and used the balance bike method. After a few runs down a mild slope, he had the balance down and was ready for pedals...although he still occasionally forgot to pedal and tipped over.
2) My second kid wanted
nothing to do with the balance bike method. He wanted to pedal, even though he couldn't balance. We went out to a parking lot, with heavy clothes, helmet and did it "old school" with lots of push starts and crashing. He's very hearty, sucked it up after each crash and kept trying. See our video. This is distilled down from about 45-minutes of crashing. After this, he was a rider.