One of the easiest ways to clog a drain is with hair, especially in the bathroom. Hair loves to stick to hair, and a big wad of it is going trap itself in your drain. For showers and bath tubs, you can actually buy drain covers that catch hair. Other drains have small holes to prevent hair and other larger debris from escaping down the drain. Be aware of what you place in your sinks, and don’t wash whatever is in there down with water.