Transplanting houseplants is only necessary when the plant outgrows the pot. It is actually the roots that outgrow the pot. Once houseplants become root bound, they can no longer absorb all the nutrients they need from the soil and they have trouble soaking up water. Houseplants don't require transplanting into a new pot often; but failing to do so when they need to be transplanted may cause them not to bloom, they may not produce new foliage or they may begin to die.
Check the houseplant to see if needs transplanting. Look for roots growing out of the drainage hole and failure to bloom or grow at the proper pace. Stick a pencil into the drainage holes---if it won't go in more than an inch the plant probably needs to be transplanted.
Choose a new pot that is one size up from the pot the plant is currently in. Pick out a pot that is the same depth as the current pot or only two inches deeper. Choose pots with drainage holes in the bottom.
Fill the pot with the same potting soil blend that the plant is currently growing in. If you don't know what blend it's growing in, use a standard potting soil or mix 1 part compost with 1 part peat moss and 1 part perlite.
Grasp the plant by the stem near the soil surface. Tap the pot on all sides with the other hand to loosen the soil then pull the plant from its pot. Loosen the roots at the base of the plant gently with your fingertips.
Put one to two inches of soil into the new pot. Set the plant inside, spreading out the roots carefully as you do so. Fill in around the plant with soil until the level of the soil is the same as it was in the old pot.
Water the plant until water runs from the bottom drainage holes. Add more soil if watering caused the soil level to sink, then moisten the new layer of soil with water.
Apply a balanced liquid houseplant fertilizer one week after transplanting. Follow label instructions for application, as this differs between fertilizer brands.