Calendula officinalis has proven to be one of the easiest plants to grow. You can start it inside to plant out in the spring or sow the seeds directly in the ground.
It prefers healthy, loamy soil in full sun. You will not get good results if you pick a shady area. It likes a little more moisture than some other plants (lavender and wormwood, for example) but does not like wet feet, so make sure the soil drains. Once established, it can tolerate a little less water and still keep producing.
The biggest key here is plenty of sunshine and once blooms begin to appear, pinch off the fully opened blooms and dry them for use. You will get an abundance of blooms if you harvest the flowers regularly.
I usually stop picking every flower as we get close to the end of the growing season. This allows several flowers to go to seed for next year!