Use the cameras near the entrance and inside the gang hideouts to help plan your strategy. Tag the gang members to get an idea of their strength and locations. Use Jammers to prevent civilians from calling the police before starting any action. Also, make sure that you have located and profiled the gang leader before starting. You can also shoot out the tires of nearby cars to prevent the target from escaping easily. When ready, lure anyone guarding the entrance away and take them out stealthily. A silenced weapon is recommended. Hide the body, then repeat for any other entrance guards. Hack available items and use explosions to cause a distraction or kill gang members. You can then stealthily take out gang members that are busy dealing with the explosion. After enough gang members have been dispatched, the gang leader will attempt to flee. Carefully knock him out while killing any troublesome survivors.