I'll add to that saying that it's a good idea to have at least a set of (2) replacement u-bolts for the rear axles. I find there's always one that the bolt breaks every time I do this.
The usual suspects (parts catalogs) carry exact replacements at reasonable cost (about $2.50-$3.00 each). At that price it's good to have because it's annoying to be stuck and unable to finish the job because one or more of them broke. Having been caught by this once, I found an alternative in a heavier piece from the universal replacement parts rack at a local NAPA or Pep Boys store. I had to drill the holes in the bottom plate slightly larger for the bigger bolt diameter, but it was otherwise an exact fit over the axle.
I would also suggest you check the rebound straps beforehand as well. While not necessarily part of the job replacing the springs, it is a good time to make sure they are not rotten or broken and that the welded attachment points to the axle are not rusted through and about to fall-off or gone already. You would have to take the u-bolts off to replace the attachment pieces, so good to know what's doing before you start.
Safety Fast!
Art