Clogged drains and pipes are a common occurrence in residential homes. Fortunately, it's relatively easy to troubleshoot these issues on your own.
If your toilet won't flush, use a plunger to push anything stuck through the system.
If your shower or sink isn't draining properly, there may be debris blocking the pipe. You can purchase cleaning tools in many hardware stores, which are designed to clear these out. Be careful not to use caustic chemicals that may damage your home's plumbing system.
If you don't have hot water in your property (or your tank isn't providing sufficient heat), check the settings on the hot water heater. You may need to make adjustments and wait 15 to 20 minutes for these changes to go into effect.