It's human nature to "save" a young animal that appears abandoned or lost. However, when a person with good intentions picks up a baby bird, squirrel, or deer, the young animal is usually as good as dead. The best option is always to leave them alone and let nature take its course, even though it's not always pretty. Often, the young animal is still being cared for by its parents and will have a better chance of surviving if simply left alone.
Unless you're a licensed wildlife rehabilitator, it is not legal to possess live wild animals. And it can be dangerous because they may carry rabies or distemper. Wild animals commonly have fleas and ticks, which can transmit blood-borne diseases, and they carry bacteria, roundworms, tapeworms, mites and other protozoans that could infect humans and their pets.
Unfortunately, fawn deer are commonly "saved" by people who find them alone and assume they've been abandoned. Most of the time, the doe is nearby, but the mother instinctively stays away from her newborn except at feeding time to avoid drawing the attention of predators. Fawns are scentless and survive by holding absolutely still, even when humans approach.
Storms may blow young birds out of their nests. If the young have feathers and can perch, place them back in a tree or shrub, away from cats or other pets. The parents will still care for them. And don't worry, they'll care for them even if you touch them. Birds have a very poor sense of smell and human touch won't drive the parents away. If you find a nest with featherless nestlings, place it in a plastic bowl and back in the tree. This will be their best chance of survival.
Enjoy watching wildlife this year, especially if you see youngsters. But make a pact to leave them alone. Let nature take its course and know they have the best chance of survival by staying wild.