Its not rocket science.
1a. If youre shipping ground, drop the tire pressure to 10-15psi
1b. If youre shipping air, you must remove the valve stem core.
2. Protect the face and back of the wheel with cardboard discs or squares. Use multiple layers on the face!
3. Use lots of tape. Tape doesnt like sticking to rubber, so youll have to start and end each pass of tape on cardboard.
4. Mark the face side of the wheel as "top" and the back as "bottom".
5. (Optional) If you have a banding gun, add a couple plastic/metal bands in case the tape fails.
Thats pretty much it.
UPS, FedEd, USPS and GreyHound will accept wheels and tires like this without issue.
How safe is it? TireRack ships their wheel/tire assemblies like this.