I initially learned to ride a bike on a grassy area (much softer falls, I highly recommend this). As I got much better my dad graduated me to the road. Everything was going great during this transition until I saw a kid a couple years older than me pop a wheelie. I thought this was awesome and being very confident in my new found skills, I immediately decided that I should give it a shot. I yanked up and back hard on my banana seat bike, I don't think my dad had any idea I was going to do this, and we both quickly learned my mistake as I tipped over backwards and my face met the asphalt. With my front tooth laying on the ground and my dad likely standing there wondering what the hell happened, I bolted home in search of my mom with blood streaming out of my mouth. I was probably about 4 or 5 at the time. So my advice is make sure the person/kid is wearing a helmet and possibly even a mouth guard those first few trips out and beware of the pop a wheelie.