Do a thorough inspection of the windshield washer system before you replace the windshield washer nozzles on your car. Make sure there's fluid in the reservoir (with antifreeze for winter months), no kinks in the hoses and that the pump is operable. In some cars, you can remove and repair the nozzles with a small needle or compressed air. Replacing them is pretty inexpensive and not too complicated.
Locate the windshield washer nozzles. Many vehicles have them clipped or screwed to the bonnet, while other cars may have them clipped to each windshield wiper arm. In some rare models, you may have to remove the cowling to access the nozzles.
Open the bonnet of the vehicle for clipped nozzles or nozzles with retaining screws that are attached to the bonnet. Locate the nozzles and hoses attached to the bonnet (most likely on the lower edge of the bonnet closest to the windshield). Some vehicles may require removing an insulated panel that is retained by plastic clips. Pry the clips out and remove the panel (if applicable).
Note the way the nozzle is attached to the underside of the bonnet. Clip-on nozzles will either be attached by a single clip on one side of the nozzle and a retaining anchor on the other end. Other clip-on nozzles may have two retaining clips that need to be squeezed together (with needle-nose pliers, if necessary). Press the clip or clips inward towards the nozzle and it will pop out of the hole in the bonnet. If the nozzle is retained by screws, simply unscrew them with the screwdriver. If there are hose clips holding the hose to the bonnet, unfasten the clips (by hand) to allow more movement in the hose-to-clip assembly.
Remove the cowling, if applicable, to access the windshield washer nozzles and attached hoses. Most models with this application will have a fairly easy cowling to remove. Retaining plastic push-pins or similar devices will need to be removed with a screwdriver or similar tool to move the cowling.
Unclip the nozzle from the windshield wiper arm for models where the nozzle is retained to the wiper arm. These types of nozzle retaining clips can easily be popped off the wiper arm by hand, and require no tools--you don't even need to open the bonnet.
Holding the nozzle in one hand, twist the rubber hose back and forth with the other hand to remove the nozzle from the hose. All nozzles have a tapered end that simply presses into the flexible hose. Because the windshield washer fluid sprays at low pressure, it does not force the nozzle off. Remove the nozzle from the hose (whichever type you have) in this fashion.
Insert the end of the new nozzle onto the hose and reassemble by reversing the procedure. Don't forget to refasten the hose retainer clips, or the hoses can kink.