some things to think about: you need more than one variety for best pollination, but the trees need to flower at about the same time. Often, nurseries have suggested cross pollinators listed right on the tags on the trees. Make sure the varieties you select are hardy for the climate zone you are in. Watch out for deer - they are a real nuisance, browsing on your trees. If you have a lot of deer in your area, skip dwarf trees, because you will have to protect them forever. Standard trees have the most yield, but are hard to pick, so most people like semi-dwarfs. It takes about 3 or 4 years to get any apples, and some varieties take a bit longer. The trees need full sun. Make sure you plant them far enough apart - most people plant trees way too close together. Make permanent labels for your tree varieties - the tags will blow off or sun bleach in a year, and you will forget which tree is which. Water the trees very well the first couple years & they are far more likely to survive. Fertilizing is worthy - they will grow faster. Consider wrapping your trees in winter against sunscald if you are in a very cold climate. I'm in Minnesota in zone 3 and have almost lost trees due to this. Read up about apple maggot traps - rather than spraying my trees, I put up red-painted balls wrapped in plastic & spread tangle trap on the plastic to catch these flies that ruin your apples by implanting eggs in the apples & then the maggots eat them. You throw the plastic wrap/baggies away at the end of the season, and re-use whatever you had for a red ball - can buy them or take croquet balls and paint them, whatever, just has to be red and kinda weather resistant.
Have fun!
