Clogged drains are just part of the joy of indoor plumbing. The good news is that you can troubleshoot the issues and prevent them from happening again, including chronic problems. But to get there, we'll need to get into what causes drain clogs in the first place.
Most bathroom drain clogs result when dirt, skin flakes, and especially hair binds to soap scum on the walls of drain pipes. Over time, this gunk accumulates and reduces water flow.
Remove and clean the drain stopper. Next, try using the humble drain plunger, keeping in mind to block the over-flow drain in the tub or sink. If that doesn't work, remove the drain elbow joint and clean it out. Clean drain stoppers routinely to prevent clogs and use a hair strainer drain-cover to trap hair before it goes down the drain.
Clogged toilets are a nasty business. These mainly happen when people try flushing down items that do not dissolve or break apart in water such as:
The plunger is the first line of defense. The most effective plungers shoot jets of water to clear the drain pipe. Many have anti-microbial coatings. Next, use an inexpensive hand-powered drain auger. While not a pleasant experience, a hand auger can reach between 2 to 5 feet down the toilet's drain pipe to break-up or retrieve things (such as Junior's action figure) that are blocking the pipe.
The best preventative for keeping your toilet free from clogs is to only put in waste and paper that readily dissolve in water. Regular cleaning will also keep water flowing smoothly.