There are a couple of ways to teach your kids to ride a bike. You have the painful option and the easy option. Both methods work.
Training wheels Option:
Training wheels are how I was taught to ride a bike. I hated the experience. I vividly remember my mom teaching me to ride and me drifting into a metal mailbox post. It hurt, it sucked and I hated it. The training wheels are bolted onto each side of the bike and the bike can stay up without the operator having to balance. Seems like a good idea, but the training wheels teach the kids a lot of bad habits and makes learning to balance doubly difficult. I did not know any better and this is how I trained my first daughter, and the transition away from training wheels was just like I remember it as a child- painful. It was difficult for me to teach her to ride. Neither of us enjoyed the experience. My first daughter was 5 when she learned to ride a bike without training wheels.
There is a an easier way, but first a little historical biking background:
I am not sure how many of you know the history of the bike, but the first bike was invented by a German man named Karl Drais in 1817. The bike was called a Draisine named after himself, or later got the name dandy horse. This bike had no pedals and the user would sit on the bike and run along with his weight supported by the bike. The bike was made almost entirely of wood and the tires were wrought iron wrapped around wheels. This was the first device that competed with the horse. These first bikes were considered a young man’s sport, as they were quite dangerous and not comfortable. It took another 78 years before the first modern equivalent bike, called the safety bike, appeared. This bike opened up biking to men, women, young and old and although the materials used have changed, the general design has remained the same.
Balance Bike Option:
The second option to teach your child to ride a bike is to use a Balance Bike (Laufrad): Once my second child came we had been living in Germany for a few years and I saw a number of the local kids using these Balance bikes. A balance bike is a bike with no pedals and is sized so that the child can sit on the seat with both feet on the ground. It is basically one of these original dandy horse bikes upgraded for modern convenience. I purchased one of these for my youngest and she loved it. First she would walk using the bike and the next thing I knew she would pick up enough speed and then lift up her feet and coast for about a 100 ft (30 m). One day we were on an errand together and it was a slight downhill slope. She put her feet up and coasted for 300 ft- I was dumbfounded. No training on my part, zero effort and she had mastered the most difficult part of biking. I figured she had the balance down and that day we would try biking. I placed her on a bike that day and pushed her and told her to pedal. First try and she was riding. For me as a parent it was no effort teaching her how to bike. The kicker is she was 3 ¾ years old. The only bad habit she learned from the balance bike was she wanted to put her feet down to stop, but this was a small inconvenience compared to the bad habits training wheels had caused my first daughter.
In conclusion, I find a balance bike the only solution to teaching a kid to ride a bike as opposed to using the training wheels. Your child learns balance first. Once the balancing is mastered then learning to pedal becomes quite simple. Additionally, I recommend that you buy one of the balance bikes used, as child only uses them 2-3 years before moving to a bike. They make the transition to a bike much easier than the training wheels. Do your part and stomp out training wheel use and teach your kid how to bike through the balance bike!