The best conditions for hostas are a dark, humusy soil that is well-drained. If you have very sandy soil, you can add organic matter, such as peat moss, to your soil to help hold water.
Soil pH is best at 6-7; the plants will utilize the fertilizers and water in the soil optimally in this range of soil acidity. At pH above 7, hostas will still grow fine, but may grow slower.
You can measure soil pH with a simple, inexpensive kit available at most garden stores, or some local garden supply stores will measure the pH of your soil sample for free. If your soil pH is lower than 6, it can be amended with horticultural limestone, which neutralizes the acids in the soil and raises pH. If pH is above 7, it can be amended with sulfur to add acidity and lower the pH.