First up is an excerpt from The Color of Your Thumb Has Nothing To Do With It.
Brown Leaf Tips Mean Too Much Water
The tips may be yellow through orange, orange-brown, to dark brown. There may be a brown band or yellow band between the green part and the discolored tip. Older and middle leaves are most often affected. Please note, tan, or paper-bag-brown tips indicate different conditions. Also, a few brown tips here and there can be attributed to aging or breakage, nothing to worry about. But brown tips over most or all of the plant, 98% of the time, are an indication that the soil is not aerating (drying) sufficiently between waterings.
Now, it is absolutely true that brown tips can mean a number of things in addition to wet soil: humidity too low or high, soil too dry, too much light, too little light, mineral deficiency or toxicity, too much salt buildup in the soil, fungus, bacteria, bugs, even breakage. However, if you're talking about indoor plants, most of the time, brown tips mean too much moisture in the soil, and that would be the place to begin investigating the cause or causes of your plant's distress.
(by Marlie Graves)