Violets are one of those rare plants that can bloom at any time of the year. This is because they are an indoor plant and so aren't subject to the seasons. Although they can bloom year round they usually need to take a break of a couple of months after each bloom to prepare for the next one.
Violets are a fairly sensitive plant, they like light soil so when potting them you need to make sure that you get a soil that is intended for violets. You will also want to make sure that you put them in a pot that is the right size, violets like a pot that is a tight fit. If the pot is too big they just don't grow very well. The rule of thumb is that the diameter of the pot should be a third of the leaf tip to leaf tip size of the plant.
Violets need a lot of light, at least eight hours a day. The biggest reason that violets fail to flower is not getting enough light. They also like to be kept in a warm humid place. One way to keep the humidity up is to put the pot in a small tray filled with pebbles and water. When watering the plant you want to make sure that you don't get the leaves wet. The plant should be watered until there is water coming out the drain holes and then not again until the soil is dry to the touch. You should add fertilizer once a month.