To keep your indoor houseplants healthy and thriving they will occasionally need to be pruned or re-potted. The process is very similar to the plants and just as important. Dead or sick branches can affect the overall health of the entire plant and should be cut off. And there is the esthetic aspect of pruning, it gives you plants a nice and tidy shape.
If you are pruning a branch off of a plant that is diseased (with fungus) it is very important to disinfect your pruning shears after using them. If you do not, and continue to prune your healthy plants there is a chance the fungus will spread to your other plants. A solution of bleach and water will kill the unwanted organisms nicely.
When you look at the plant if it appears too full you can thin it out, this is important around the base trunk or stem. You want good air circulation around the plant and if the branches and leaves are too congested this will not happen. Trim enough of the excess foliage away to let the plant "breathe". When you are trimming branches to keep a uniform appearance to your plant just trim what is necessary. Prune the new growth to keep it inline with the rest of the plant.
As plants grow so do their root systems. If your plant isn't thriving or you notice that the roots are visible around the outside of the pot, your plant is most likely root bound. It is important to transplant the plant to a larger pot. Once you have chosen one and have prepared it for the plant very gently loosen the roots on the outside of the root ball. Then put the plant in the middle of the new pot surrounding it with new potting soil.