I never met an avocado pit that didn't grow. And the seeds are so
gorgeous, I find I cannot part with them (but don't buy many
avocados). But one grew in the middle of my compost heap til the ice
storm got it.
I've always started them as you noted: 3 toothpicks to hold up the
seed in a small jar with water level half way up the seed. The roots
appear first.
Kira