[flybouy]

Great advice from all the responders. Having a clear lense and fresh lamps with a properly adjusted headlight can make a huge difference. Headlight aim should be checked after replacing lamps to ensure proper alignment. This is the most economical solution.
I can add my experience. After a lot of blog reading and research I retrofitted both of my trucks with aftermarket headlights, my F150 King Ranch with halogen and my F250 with HID. Both sets of headlights are aftermarket with DOT approved certification. I have used the SYlvania Silver Stars as well as the Phillips equivalent and they don't last long. DOT mandates 55 watt max on halogen low beams so the mfg accomplishes this by a coating that reflects the light back into the lamp and focuses it back out. This increases heat in the lamp hence the shorter life. If you travel a lot at night or have daytime running lights then prepare to replace them more frequently at an increased cost. The HIDs have been in my truck for 4 years and still going strong. The down side of HIDs is that factory headlamps are not designed for them so the beam pattern is scattered causing issues with opposing traffic. If you use HIDs then you should use a headlight housing designed for HIDs, typically a projector style. HIDs also require extra wiring for ballasts and can be an issue if your challenged for space under the hood.
With the 2 examples above let me say that they are both expensive. With a truck that's 17 years old you may not want to invest that much money.
I know this is a long response but I hope it helps.