Listen to the gardeners talk:
"Two things you should do: Plant the dahlias in full sun and don't slack off on staking them. Let me tell you, if you put them in a semi-shady area and sort of forget about them, you'll come out in midsummer and find a floppy pile of leaves and flowers, and you'll be so disappointed. I mean, really, really disappointed."
"Here are some bachelor's buttons and the prettiest low, purplish monarda. This monarda isn't a thug at all. It'll stay where you put it. You'll plant the bachelor's buttons, they'll dry up and disappear, and you'll think, 'Oh, no! I killed them!' But don't worry, they'll show up."
"Just keep on pinching them back until July Fourth. You won't want to, because they'll be looking nice and full, but pinch them about every three weeks until July Fourth. If you pinch them again a little after the Fourth, well, that's all right, but try not to do it too late. They'll be bushy and full of flowers come September."