The old standby to teach your child to ride is to lean down and push them. With the stingray bicycles you used to have a nice handle to hold while you were running.
This was never been optimal. There are several problems. One, your child becomes dependant on you holding them up, two if you let go they usually look back to see if you are holding them up and fall down. If they turn sharp while you are running with them they can fall in front of you. When you fall on top of them it hurts both of you. It is really hard to run while you are leaning down.
Start with the helmet. Make sure your child's helmet fits them properly and will not fall down and block their vision. They must learn from the start that they can only ride their bike with their helmet. Shoes should not be sandals, flip flops or open toed. Long sleeve shirt and long pants are a good idea when first learning. Gloves will save their hands if they fall.
There is a Simpler Way
Do not run behind the bike pushing your child. Start by finding a very gently sloping unused road or driveway. Take the pedals and training wheels off the bike. Remember the left hand pedal will be threaded backwards. Put the seat height so your child can easily touch the ground on both sides of the bike. Now let your child go up and down the gentle slope by using their bike as a hobby horse. They will quickly get the feeling of gliding down the slope with their bike.
Coasting down the Slope
Get them to go down the slope holding their feet up. Make sure the slope is gentle enough that they do not gain speed. The slope should be just enough to help them coast. If you have your bike do the same thing with them, you can show them how to coast and run over the pebbles you have set out. When they can hold their feet up and turn the bike to run over the pebbles they have mastered balancing and turning a two wheeler. Play at this for a while and get them turning both left and right. Add pedals and have them start by going downhill and pushing with their feet. Once they are moving have them start pedalling and they have it mastered.
Safety on the street and sidewalk
Your child needs to learn the traffic laws and that cars cannot see them so they need to look for and avoid cars. Remember many car bike accidents happen on sidewalks with cars pulling into and out of driveways.
Safely Teach your child to ride without training wheels.
Your back will not be sore, you will not have concrete burns on your hands and knees from falling over your child's bike. This is easy and it works great.