Location: Avoid locations with poorly draining soil.
Where you plant a perennial is as important as what you plant. Avoid any location that stays wet. This is any soil that gets consistent moisture and doesn't drain well. In well-draining soil it is hard to provide too much water to a perennial in the summer but during the winter is a different story. When the soil freezes in the winter water must run off and away from the plants because there is no way for it to soak into the frozen soil. Avoid planting at the end of your downspouts. Even the smallest amount of snow melts from your roof and runs what could be a lot of water out of the downspouts and onto your perennials. Avoid planting in locations where you pile all the snow from winter storms. The snow cover is good for perennials because it protects them from the winter cold but if all that water created from the spring melt can't drain away it will kill the plants.
Soil Type: Avoid heavy soils or amend with compost.
If the soil you are planting in has moss growing on top of it you must realize this is a spot that is shaded and consistently wet. The best thing to do with this location is either rock it or amend it. All perennials will resent a wet winter soil and they will crown rot. They turn to mush and die. Heavy clay soils can also be big problems. Rock it or amend it. Plants like mums will die in heavy clay soils. You can amend the soil by digging or tilling the area and working in products that improve aeration and percolation of water. Sand, gravel, and certain composts work well for amending a heavy clay soil.