For many people, the cost of a spray in liner is prohibitive. Then there are those, such as myself, who can afford a spray in liner but can't stand the thought that you can do it yourself for less (ie, I'm cheap!)
Since the bed of our 2000 Ranger was starting to get scrapes, dings and scratches, I figured I'd better go ahead and install the bed liner before rust starts forming. I choose the Herculiner kit, available at most auto parts stores.
The first step is to take off the tail gate of the truck. The procedure varies from truck to truck. On the Ranger, undo the clips on both sides, lift the right side off the hinge and pull the tailgate to your right, sliding it out of the left hinge.
Next, apply masking tape to the edges of the bed. I recommend using wide tape to prevent getting bed liner material on the bed rails.