Is there power? Check the power cord and look for LED lights showing there is power.
Is there paper in the printer, or a paper jam? It will not be able to print if it's jammed or has no paper.
Is the printer shared through another computer?
Click start, and go to devices and printers.
If the printer you are trying to print to says the printer name, followed by a computer name (example: HPLaserjet2015-Reception1) then you have to ensure that the corresponding computer is up and running.
If it is a network printer, check that the ethernet wire is connected.