Using a water heater pilot light igniter is easier than matches or hand held lighters. Many newer models have them. You just have to follow the instructions and then depress the button a few times.
Not sure if this is what you need to do? See the article on 'Gas Water Heater Troubleshooting' for a complete list of problems and thier corresponding solutions.
How To Tell If You Have an Igniter
A water heater igniter has a sparking tip that is directed at the location of the pilot light. You should be able to see it above or next to the gas supply line for the pilot light.
The other tell tale sign is the wire that runs from the gas valve to the igniter. Most water heaters do not have any wires attached to the gas valve.
The igniter is also likely to have a separate button that has to be pushed to engage the sparker.
Following the Instructions
The lighting instructions are different on each water heater. Read the instructions and follow the steps. You will usually turn the dial to pilot and hold down the button. Then press the igniter until the pilot lights. Hold the button down for as long as it tells you.
See the article 'Following Pilot Light Lighting Instructions' for information on how to locate the instructions and why it is important to follow them.
The first thing you will want to do turn the temperature setting to its lowest position. Then turn the gas vavle to 'Off'. You should wait about ten minutes before you do anything else. There may be some lingering gas that you want to dissipate before you try to light the pilot.
The next step is to remove the outer cover from the burner assembly. It should snap off. There is a small view window that allows you to see the pilot light. Make sure it is cleaned off. A small flashlight would not hurt at this point.
Watch through the glass and make sure the pilot stays lit. Wait the proper amount of time and turn the gas valve to on. After that you can set the thermostat to the desired temperature.
If the water has been off for any length of time the burner should light right away. Make sure it is burning properly and replace the outer cover.
What If the Pilot Light Does Light
Normally you would get concerned if you followed the instructions and the pilot light failed to light. With an igniter, you may have a problem with the igniter itself. If you have ever used the igniters on a gas grill, you know what I am talking about. They are not always the most positive lighting method.
You can still light the pilot light using a traditional match or long lighter method. You will still need to follow the instructions and go through the procedure again. See the article on 'Manually Lighting a Pilot Light' for more information.
If after you have tried the traditional method, you find that the pilot light won't light or won't stay lit, you likely have another problem. See the article 'Problems With Water Heater Gas Valves' for a pilot light that won't light at all. For those that won't stay lit, it is likely the thermocouple, see the article 'Troubleshooting Water Heater Thermocouples' for instructions on what to do.