The best time to buy mums is now before they are in full bloom so you can enjoy them for a longer period of time.
Mums like regular conditions. They will not thrive in conditions that experience vast changes in temperature. Mums do best outside in full sun.
Use your hand to check the soil every day. If the top inch of the soil is dry, water your mums and let the water drain out the bottom of the pot. If you have a saucer that catches the drained water, make sure to dump the excess water out. Prune off dead flowers to encourage more blooms. Mums are perennials, so you can plant them in the ground and over winter them. They are hardy and don't need a ton of work to over winter. You can cut them back, but doing so is unnecessary. There you have it! Easy, vibrant color!