Yes, you can grow an avocado from a supermarket seed. The toughest kind to grow are the ones with a smooth green skin. I don't know if it because they are to young and undeveloped or what. But , they can be coaxed into producing too. The easiest way to deal with the germination process is placing the seed in a baggy full of sphargum moss. Dampen it but not drowning, set it in a warm spot. In a week or so it will sprout. If the bag condensates open it for a day to keep the plant from rotting. When the roots start to grow and the leaves show, transplant it into a moist medium. Wait for the roots to get to 3 or 4 inches in length. Don't place it in direct sun. They like bright spots though. Keep the medium moist, not wet, at all times. They need a little down time from about the fall equinox to after the middle of January in the Northern hemishphere. You can put a bunch in a big container for visual impact. You can pinch them back to make the plant bushier. If you live in a warm area without freezes you can plant them outside and sit back and wait a few years and pick your own. I always had to add activated charcoal to the ones I started in water to keep it sweet. The same as in the baggie, plant in soil when the roots are 3 to 4" long.
Master Gardener. I just picked up a book from Hamilton Booksellers on line out of Ct. for less then $10 total, by Debrora Peterson and Millicent Selsam called "don't throw it, GROW IT !". They cover a lot of things in depth that will help with starting plants of all kinds from table scraps. They cover everything from Almonds anise to papaya, peanuts guava and about 70 more common household plants. Most of the above information is from their book. Even master Garadeners are on the lookout for great additional information to add to their fun. Have fun ith your new Avocado plant. This book is dynamite.