Growing apple, pear, cherry, plum, and other temperate fruit trees from seed is challenging only until you know a few of the secrets. These methods will also work for nectarines, apricots, pawpaws, quince, persimmons, and most any commonly cultivated temperate fruit bearing tree as well as grapes and many berry bushes.
The best approach is to take freshly collected seed, clean any remaining fruit pulp from it, and place it directly into a growing medium. This can be a pot of soil, or a plastic ziplock bag with a moist paper towel. In either case it is desirable to avoiding letting the seed dry out any more than is necessary.
The seed then needs to be held at approximately 40F for anywhere from several weeks to several months. For most species simply placing the ziplock bag in the refrigerator in the fall, and removing it in the spring, is sufficient. Most refrigerators operate at something between 35F and 45F, which is just about perfect for breaking temperate fruit seed dormancy.
If you’ve planted the seeds in pots, and your climate is suitable for growing the trees in the first place, you can place the pots outdoors in a sheltered spot under a tree or such. In this case you might want to use window screen or something similar to keep rodents from digging and eating the seeds and young shoots.
Freezing does not hurt the seeds, but it also generally does a poor job of breaking dormancy in the seeds.
In the spring, if the seeds have not already sprouted while cooling in the fridge, they will soon sprout in the warmer temperatures.
From the time you pull the seed from the fruit, until the time you plant it in your garden or orchard, you want to keep it moist but not soaking wet.
Best wishes, and good gardening!