There are many varieties of cacti from barrels to uprights and from very thorny to very hairy.
Many of the cacti will bloom although most of them need to be about 3 years old and pot-bound to bloom. They need good care in the growing season and neglect and cool temperatures (50 degrees) in the winter.
LIGHT: Cacti like a sunny location, especially in the winter. In a greenhouse location they may need some shading from the sun.
WATER: Cacti store water in their thick fleshy stems or leaves, therefore they can tolerate a great deal of neglect. The hardest thing for a cactus to tolerate is too much water. During the winter they need only enough water to keep them from shriveling.
When repotting cactus use a pot that is only slightly larger that the one you're removing it from. Repot in the spring at the beginning of the growing season.
Cacti can be propagated from cuttings. It is best to do this in the spring or early summer. You should let the cutting dry for 3 - 10 days before placing in a light compost.
Cacti are readily available in 3" or 4" pots. On a seasonal basis, they are available in larger pot sizes.