Fines for traffic offenses vary by state, but in general, many of them follow some basic similar guidelines. A ticket for failure to use headlights or driving without headlights on on can typically result in a fine ranging from $130 to $200, and also often results in mandatory attendance at traffic school, along with the accompanying fee for the classes, which can range from $50 to $75.
Typically, there is no excuse for driving without your headlights on in the dark or in conditions that otherwise require their use, so it's not often worth your time to attempt to defend yourself against this charge – unless, of course, there is a genuine mistake and you were not driving as the charge indicates, or unless there were extenuating circumstances (such as malfunctioning headlights, and you were simply driving your car slowly home, or something similar).
Keep in mind that the fines, fees, and penalties for this type of charge, as with any moving violation or traffic charge, can and will vary not only based on your state, but based on the specifics of the situation as well as your past driving record. Anyone with prior offenses may be facing a stiffer fine, and if, for example,you were driving without your headlights in an area of heavy traffic, the penalty may be more severe than it would have been if you were simply rolling your car home through quiet residential streets at a slow speed.
To find out exactly what fines you are likely to face, and for further details regarding how to defend yourself and keep your driving record clean, consult with a lawyer.