Changing a headlight bulb is normally a quick and easy process. There are many different types of bulbs, each identified by a number. The first thing to do is to determine which headlight is out and get a replacement. It is essential that you use the proper bulb as otherwise you may sacrifice nighttime visibility or blind oncoming drivers. The next step is to disconnect the wiring going to the bulb. The connectors normally pull straight out, however there is often a tab that must be pressed before the connector can be removed.
On newer cars only the bulb itself needs to be replaced. They are normally accessed from under the hood, usually under an access panel that needs to be removed or behind a flap that can be moved out of the way. The headlight bulbs are held in place with a retaining ring behind the light that needs to be unscrewed in order to free the bulb. Take note of the orientation of the bulb and retaining ring so that you can replace them in the same position. Pull the old bulb out, and insert the new one being careful not to touch the glass surface of the bulb. Oil on your fingers can create hot spots on the bulb that can cause it to fail. If you do accidentally touch the bulb you can clean the surface with rubbing alcohol on a clean lint-free cloth. Replace the retaining ring and access panels.
Older cars use sealed beam headlights where the entire assembly needs to be replaced. These headlights are normally kept in place by a retaining ring on the outside of the car. The retaining ring is usually held in by screws that once removed should allow the ring to come off and let the headlight to slide out. Install the new headlight in the same orientation and replace the retaining ring.
Once the headlight has been replaced reconnect the wiring and test the headlight to ensure that it works properly. If the headlight still isn’t working properly the replacement bulb may be defective or you may have a fuse or wiring issue. Headlight bulbs slowly get less bright with age which accounts for some of the difference noticed when upgrading to more expensive bulbs. You may want to try a new set of regular bulbs to see if this makes a difference and if so get into the habit of replacing the bulbs before they burn out.