Some plants require soil to be acidic or alkaline in order to thrive. You can buy a pH testing kit, but this DIY method gives you an idea of what kind of soil you have using two ingredients you probably have in your pantry: vinegar and bicarb soda.
Picture: Dwight Sipler/Flickr
This "quick and dirty" method won't give you a specific pH reading, but you'll be able to tell if your soil is more alkaline, acidic or neutral:
Vinegar: Take a sample of dry dirt (about 1/4 cup), mix with distilled water to make a liquid "mud" and then start pouring household vinegar over top. If the mixture fizzes, it's alkaline.
Baking soda: Mix dry dirt and distilled water as above then start sprinkling baking soda over top. If the mixture bubbles, it's acidic.
If neither test produces a reaction, you have fairly neutral soil.
With that newfound knowledge, you can plan your garden appropriately or take steps to amend the soil using Tipnut's recommendation in the link below. (So even if you have alkaline soil, you can give your azaleas the acid soil they crave.)
How To Test pH Levels In Soil [Tipnut]