Please contact your local county extension office and see when they have a class on fruit tree care & maintenance scheduled. It's more involved than trimming.

Citrus require minimal pruning and would be fine if you do none at all. For the peach and apricot find a course or a guide book.

The main thing to watch for is that the rootstocks doesn't sprout. If allowed to grow, rootstock shoots can outgrow and out-compete the edible variety grafted onto it, and even kill it. So there's that.

Next, pruning may involve opening up the center and pruning out branches that cross and/or rub. Then, you'll want to consider what shape you want your plant to take on -- do you want to train it as a rounded shrub, or as a tree with a trunk?

If you can post pics, that might help.

Location might matter as well. If citrus leaf miners are in your area, you want to time your orange pruning so that you don't have new growth when the adults are laying eggs or your leaves will look mangy.

(I agree that orange pruning isn't really needed unless you're trying to maintain a size or shape--and that's often the case since oranges are usually pulling double duty as ornamentals.)