The most common cause is hot air - if yours is near the tv, a heat source or a computer or anything that produces heat, that would make this more likely. In theory, insufficient fertiliser is supposed to be a cause, but I never feed mine and there's not a brown tip to be seen.

Low humidity--often associated with a heat source--drought, and/or sodium in the soil or water are the commonest causes. Excess fertilizer can burn the leaves, but that usually causes 1/3 or more of each of the youngest leaves to turn black.