Most azaleas prefer a moist, loamy, acid soil which is tough to come by naturally in this area of the Midwest. Anytime you can work some cotton bur compost or sphagnum peat moss into the soil would be very beneficial. Just be sure to gently incorporate these amendments so you don't disturb the roots too much.
Some acidic fertilizer like Hollytone or something similar, would be great. Lowes, Grass Pad or any other garden center will carry fertilizer specifically for hollies, azaleas and rhododendrons. Most are granular and you sprinkler around the base and water in once or twice a year. Follow the directions on the bag. It's worth a shot! Hope that helps!!
*Special Note- I do not use azaleas very often in my plans because they are a touchy plant in these area. Our climate and soil conditions don't allow any plants in the rhododendron/azalea families to thrive here unless special considerations are made. These things be done done in my opinion to successfully grow Azaleas in this area.
1) Locate the bed in a shady protected area. Dappled shade is best, protection from hot, afternoon sun is a must. Also, shield from drying northwest winter winds makes a huge difference.
2) Amend the soil in the bed before planting with compost and peat moss.
3) Do not trim in fall or early spring
4) Fertilize twice a year- Hollytone or similar
5) Supplemental watering during hot summer months and dry, winter months. ALL evergreens need moisture even during the winter to survive and thrive.
Finally, when shopping for a new azalea, always, always, ALWAYS read the tag thoroughly. A lot of varieties are only hardy to zone 6. Our winters in Kansas City sometimes get down to below zero, which is zone 5. What good is a reblooming azalea if it dies every winter? Also, their are some really great varieties of deciduous azaleas, like the Northern Lights series, that are fantastic, hardy options for us, because they were developed in Minnesota. Just food for thought. Have a great week!