Decide what trees you are going to plant and purchase them in advance.
This year I decided to add Pawpaw, Persimmon, Nectarine, Fig, and Pomegranate trees to my little orchard. I also needed to replace an apricot and a pecan tree. If you want fruit trees, you usually need to purchase at least two for cross pollination. Sometimes you can get a self-pollinating tree, but they still tend to perform better with another tree in the area. Without cross pollination, the tree will grow, but not fruit. Another consideration you need to make is how old of a tree will you purchase. The younger the tree, the cheaper the price, but the longer it takes to mature to a fruiting age. I try to purchase trees at about 3 years, they're not too pricey (usually the $20 range) and they will produce in 2-3 years. If I were only purchasing 2 trees, I'd probably go for an "instant orchard" when they are about 5 years old and are about $50 range. I order from a company in Georgia, Willis Orchards, and have had good luck with their products for the most part (about 90% success rate). I usually place all of my bush, vine, and tree orders in the late fall - early winter in anticipation of a winter delivery.
Decide on the timing of your delivery
Typically, you can plant fruit and nut trees in either the Spring, before the plants are in full bloom, or the winter, while they are dormant. I've tried both ways and have found I have better luck with winter plantings. I order my fruit trees from Georgia, and their Springs tend to be warmer than ours here in New Jersey. Cold snaps have sent some of my blooming young trees into shock, and they didn't make it. I've had pretty consistent good luck with all of my winter plantings.
Prepare for the arrival of the trees
Because New Jersey gets pretty cold in the winter, and the ground freezes, I prepare for my trees' arrival before the ground freezes. I will plot out where I want them to be. I have planted my trees around the barrier of my yard to make a natural fence, and then added a second layer of trees 8 feet away and staggered the trees. You want to make sure that you dig a deep enough spot for the root ball. It is not fun to break new ground in 10 degrees. Better to dig too deep, than too shallow. When ordering nut trees, the root ball is significantly larger than fruit trees, so prepare accordingly.
Plant the trees.
Once the trees arrive, unpack and plant as soon as its feasible to do so. They are usually packed well with plenty of nutrients to survive well for a few days, but personally, I don't like to push my luck. I want to unbox them and get them into sunlight and soil as soon as possible. Be careful removing them from the box and unwrapping the root ball. Place the root ball into the hole, and back fill with soil. Stomp down at the base and ensure that the tree is solidly in place. Water generously.