Clogged Toilets
If your toilet won't flush properly, there is likely something stuck in the system. You can typically use a plunger to unclog the toilet and push the clog through the pipes. Be careful not to flush your toilet until the clog has been cleared, as you may otherwise cause the toilet to overflow.
Showers/Sinks
Most shower or sink clogs are caused by hair and other debris getting stuck in the pipe. You may be able to clear out this debris using a drain cleaning tool, sold in many hardware stores. Please refrain from using harsh chemicals to clean the drain, as these could potentially damage your plumbing system.