What should I use to mulch my azaleas? Should I amend the soil at the time of planting?

You can mulch azaleas with shredded leaves, leaf mold, pine needles, or pine bark mulch. Don’t use shredded hardwood mulch since it often drives the pH upward. Pine bark is especially useful since it can lower the pH where it is too high, but it is best used on relatively flat ground since it’s light in weight and tends to float away in heavy rain.
You only need to amend the soil if it is devoid of organic matter or if the pH is too high. Have a soil test done by your local extension service to determine if something needs to be added. A light amount of well-decayed organic matter dug into the top layer of soil is helpful for retaining moisture and preventing compaction.