There are 2 possible causes for your printhead on your ink printer to dry out (this is not to be confused with blocked nozzles in the printhead).
Number one is not using your printer frequently enough! Try and use your printer at least once a week. Print out at least a couple of lines of text in both black and colour to keep the ink flowing through and the nozzles ‘moist’.
Number two reason is using incorrect ink. Some refill and generic inks are not formulated correctly and do not contain the special ingredients needed to stop ink drying in the nozzles in too short a time. Genuine brand name inks contain thinners, lubricants and solvents to prevent the ink drying up in the nozzles too quickly. Once on paper, these thinners, lubricants and solvents dry up quickly without affecting the print. If you are having problems and suspect it may be caused by the ink, buy a set of genuine cartridges and install them in your printer.
Clearing blocked print nozzles will be covered another time.