The process for planting is pretty similar whether you're planting in the ground, beds, or containers. Just make sure your soil is fairly light and spongy and full of nutrition such as compost and/or manure (Most manures need to be aged to avoid nitrogen burns to your plants). They also like sandy soil, but sand isn't a necessary amendment. Seeds can be planted well before the last frost date, 2-3 weeks prior is a safe bet. Your last frost date can be found on your search engine of choice. Beets don't like the transplanting process much, so it's best to sow them directly into the ground, bed, or a container. (Containers work best when at least 12" deep, but don't be afraid to try a shallower one)
Seeds should be planted about an inch deep. The plants will need to be thinned to about 3-4 inches apart for larger cultivars, and 2-3 for smaller ones, but feel free to plant closer initially to allow for some failed germination. If you're planting in rows, they should be 12-18 inches apart, but if you're using the square foot gardening method, you can simply space them 2-4 inches on every side. Never be afraid to experiment with different spacings to see what works for you. Gardening is an art!
Water immediately after planting, and if possible, water lightly every dry day until you see sprouts. Then they need a minimum of one inch of water per week. (In other words, water fairly deeply 1-2 times a week if it doesn't rain). Mulch is highly recommended to retain and slowly release water. Grass clippings, hay, leaves, wood chips, etc all work as mulch.
In 7-8 weeks, your beets should be ready for harvest! Not only can you harvest the root, the leaves are a delicious addition to salads, sandwiches, and other dishes. You can use the entire plant, much like turnips and radishes. Since you don't want your beets all at once, space your plantings. This could be a few seeds every day, or a new row every couple of weeks. It really depends on how much you like beets.
Come summer, you'll likely reach that sad point where they don't do very well. But never fear! You can plant them again in late summer/early fall, and grow them well into the winter.