in a perfect world you would have 2 floor jacks and jackstands.
I only have one jack. what i do is put one side on the jackstand at its lowest position, then do the other side to working height, go back and raise the first side. Sometimes when lowering the jackstand may lift up a little so lower slowly and observe the stands. When i first got my jack i wasnt used to how fast it released, the saddle popped off the rail and pushed in the floorpan. Rubber mallet and dolly fixed that one up right away but it sucked nonetheless.