We did this all the time as kids. I thought everyone did.

Stick 3 toothpicks into a pit that hasn't been refrigerated and place it over/in a jar of water. Like a pickle jar or a peanut butter jar. Keep the water about halfway up the pit. It does matter which way the pit points, but I don't remember. My recollection is point up.

Once you get roots, let the water level lower a little bit because the pit will sometimes rot and it can get stinky (unless you like that sort of thing).

They can get tall and leafy. I think though, that if you want big avocados you need to graft a proper variety.

It is as exciting as sprouting a sweet potato!

I grew up in a sticker patch between an orange grove and an avocado grove.
Maybe they were the good old days, but I don't miss the snakes and the occasional wrap of barbed wire around my ankle.