In the container shown below, I have planted the following: Dracena (spike) (1); Osteospermum (1); Zinnia Profusion White (2); Zinnia Profusion Orange (2); Purple Scaevola (1); Cuphea (2).
Zinnias do benefit from plenty of water but if you walk out one hot day and see them wilted, do not despair because they are as forgiving as they are prolific. Just give the pot a good dousing of water and if you have to, cut off any stems that did not survive the neglect. They will bounce back and continue to bloom happily for the rest of the season.
Bookshelf: Container Gardening Books