Hydrangeas relish really rich soil, gentle morning sun, and protection from strong sun. If not planted in the right spot, they can be problem prone so here is a link to our pest management web page.
Avoid sunburn by providing shade and proper cultural care, especially adequate irrigation. Appropriate irrigation before discolored leaf tissue is killed can usually restore the green color to sunburned foliage.
Cut off dead flowers after bloom, just above the new sets of leaves.
If you are trying to grow hydrangeas indoors, try a well lit window facing east.
The amount of fertilizer used per plant will vary with the size of the plant. It is much, much better to err on the side of too little fertilizer than too much. A very small plant will take about 1/4 cup. A very large shrub will take 1 - 2 cups spread around the drip line of the branches (not next to the trunk).
Don't fertilize a plant that looks sick or wilted. If a plant is struggling due to a disease or root problems, the fertilizer will only add stress to it. Try to cure the illness before adding fertilizer.