Keep your gate well-lit. Place garden lights near your gate and ensure that street lights are functioning. Vandals are less likely to damage property if there is higher chance they can be identified in bright light versus a dark area or in shadows.
Keep your gate clean, working and graffiti-free. If your gate is broken and covered in graffiti, it is far more likely to attract more vandalism and debris can be used as a tool for damaging your gate.
Encourage neighborhood involvement. The most effective way to fight any kind of vandalism is to get your community involved. Set up a community watch and patrol your neighborhood, or set up an alternative space for graffiti artists to practice spray painting. If you are friends with people in your neighborhood, they are also less likely to vandalize your property.
Set up security cameras near your gate. This will help you catch vandals and discourage people from damaging your property. If you manage to catch vandalism on film, give the footage to the authorities.
Keep your gate secure. Install stronger hinges and handles and keep your gate locked at all times. Vandals will move on if your gate presents too much of a challenge.
Keep your eyes open. If you see suspicious behavior in your neighborhood, call the police. Do not approach vandals directly as it may lead to physical conflict.