Just be very careful, and sterilize your tools between trees. Look up common diseases like fireblight and Cherry Leaf Spot and learn how to spot them. With Prunus, an ounce of prevention is really worth a pound of cure.

If you want to air-layer, the best time is probably going to be early summer (unless you get really hot dry summers; then do late spring). You ring the shoot (you can leave a small section of bark across the gap if you want, and that can keep the shoot from dying back, but FYI that can also sometimes make the graft wound just heal over instead of make roots). Wrap a nice wad of damp sphagnum moss around the wound, then wrap that in plastic, and tie the plastic firmly but not tightly to the branch both above and below to seal in moisture.

You may need to drip some water into the bag of moss if you have a drier spring; the moss should be damp at all times but not soggy. Wait a few months and you should get roots.

That being said, rooting cuttings and grafting tend to be much more successful with Prunus. Some trees just take to certain propagation methods better than others.