It might be time to give your plant a change of scenery after a year or two in the same pot. After approximately this time, the plant will have taken all of the available nutrients from the soil and will have reached a growth plateau; if it doesn't have any more food to eat, all you're doing is watering it to keep it alive.
You'll need to repot the plant with new potting mix if you want it to thrive. You can go up a size if your plant has been in the same pot for more than a year. However, don't increase the diameter by more than an inch. Giving the roots too much more area at once will cause them to become overwhelmed. When there is too much soil in relation to the plant's size, the soil will retain a lot of moisture. If the roots remain damp for an extended period of time, root rot can develop, which is bad for the plant.
It's time to get your new potting mix ready after you've chosen your new pot. Inquire about the best indoor potting mix for your particular plant at your local nursery. Various plants will require different amounts of nutrients. Succulents, for example, require a lot of sand in their mix. Add a dollop of seasol to the mix for further protection. Fill the new pot with a layer of the mix, about a third of the way full. This is where your plant will be placed.
Now it's time to take the plant out of its old pot. Grab the plant by the stem or stalk as close to the top of the soil as possible. Hold on tight and bounce it around a little to loosen it up. It's easier to squeeze the bottom of a plastic pot. When you start to feel some give in the plant, slowly raise it up.
Once it's all gone, give the roots a little massage to get rid of any remaining old, dried dirt. The plant can then be placed in the new pot. Fill up the gaps around it with the rest of the potting mix, making sure it's snug - you don't want it to droop later if it's a particularly big or large plant.
For a few days, your plant will be surprised; a large change like repotting can be rather stressful for it. Make sure it gets plenty of water and keep a watch on it for the following few weeks to determine whether it need any additional attention.
Repeat with all other plants that require it as needed. Good luck with your planting!
A Step-by-Step Guide to Potting