The "recommended" lift point is the lower shock mount, but that usually winds up bending the U-bolts since they stick down below the mount.
You can usually just lift on the axle tube itself. I use a block of wood on the jack instead of the metal saddle, or if you have a rubber/poly jack pad to cushion the axle that works too. You can just use the metal saddle, and the raised points of the saddle keep the jack in place, but I think it's better to use something like wood or a cushion that will deflect from the weight, and create it's own form so it won't move at all.
Be sure to chock the front wheels and you should be good. You can use scrap 2x4's or similar objects to chock them. Kick them towards the tire tread so they are snug, chocks in front and back of the tires might give more peace of mind if you need it.
It can also be easier to loosen the lug nuts while the vehicle is on the ground, but with the rear wheel you can set the parking brake and that will keep the wheel from rotating so you can loosen/tighten the lug nuts without the wheel turning.
