Toilet Clogs
If your toilet clogs and won't flush, use a plunger to push any clogs through the pipe. If the toilet still won't flush, you may also want to lift the cover on the tank to make certain the chain is still correctly attached.
Drain Problems
If your sink or bathtub isn't draining, you can use a plunger on these drains, too. Many hardware stores also sell drain cleaning products you can use to dislodge anything stuck in the system.
Please be careful when using cleaning chemicals, as corrosive liquids may damage the pipes.