Try to pick a spot with as near full sunlight as possible-performance will vary indirectly with the amount of shade. Select a location that provides good drainage.
Glads do well in a wide variety of soil types.
If you've grown a good vegetable garden, follow pretty much the same program and you should have excellent results. Glads like a pH of 6.2-6.5. As a precautionary measure a preplanting dip is advisable, a good fungicide, such as captan, mixed with an all purpose garden insecticide will do. Your first planting can be made as early as the ground can be worked. Subsequent plantings should follow about 10 to 14 days.