Fences should be of a certain height to divide your driveway from your neighbor's property or from the rest of your yard, but they shouldn't be so tall that you can't see over them when backing out of your driveway. This depends on what type of car you're driving and also what type of street you live on. If there's a sidewalk or regular foot traffic past your driveway, you should design the fence so that it offers you a decent amount of privacy but also allows you to see over one end of it so you can spot pedestrians walking by. If the street you live on is reasonably busy, the fence should also be low enough so that you can see passing cars so as to not cause an accident when backing out of your driveway.
There are a number of materials with which to make your driveway fence, and all of these should be considered when preparing to install it. Metal is the most durable but will entail the most construction, because the pieces of metal will have to be secured in the ground or in the driveway. Wood will break down over time but will still be fairly durable, and will cause less damage to a car that accidentally bumps into it. A hedge, or fence made from foliage or bushes, will do the least amount of damage to any vehicle, but must be kept up from season to season so it continues to grow and work as a fence line.
For fences on driveways, especially long driveways, lighting of some kind should be planned for along the driveway and the fence line so you can guide your automobile along without hitting anything. Christmas lights can be strung along some fence lines if they fit with the decor and look of the house, and you can install reflectors or solar-powered garden lights along the base of the driveway fence. The right lighting plan will allow your driveway fence to be seen at night, while also making the entrance to your home more welcoming and attractive.