The January/February 2010 edition of Chicagoland Gardening Magazine has an article about how to grow an avocado (Persea americana, Lauraceae) from seed. I know a lot of people have done this but I don't think I ever even saw an avocado when I was a kid, and now we don't like avocados so we don't keep them around. However, I have been known to grow things I don't like to eat, including strawberries, hops, and green beans. Sometimes TMCH eats the results, and sometimes I just like the plant. I tried to grow a mango last year, but instead I grew a nice crop of mold. The avocado will go better, I just know it!
The first step: wait for the avocado to ripen. I am using a Hass avocado, and today it was black and soft, definitely ripe. I cut through the rind and the two halves fell apart easily. The avocado fruit is a berry.
I scooped the seed out from the pericarp with a spoon and washed it with water and a sponge to get all the icky off it. The surface of the seed is beautiful, like marled wood. It's about 1 1/2 inches long and slightly egg-shaped.
I then poked three toothpicks into the soft surface of the seed, about 1/3 of the way from the top, the top being very slightly more pointy than the bottom, and suspended the seed over a glass. I filled the glass so the water is 1/3 of the way up the bottom of the seed, and wrote the date on the glass.
I put the glass in a south-facing window. It needs 6 hours of daylight a day. If it doesn't sprout roots in 6 weeks I will have to start over, but hopefully something interesting will happen soon!