Staying stationary is writing your death certificate...especially in a uav and scan environment since you appear to be playing vanilla bf2. The best approach is to always place yourself behind friendly infantry. Not right behind them on the frontlines but maybe 50-100 meters behind them in a position where you have overlook. They act as the shield as the enemy has to focus on them while you cover them from afar. Your position should not be stationary lying down and going on typical roofs is the first place people look. What works best is using the terrain...use it to limit enemy line of sight while focusing yours and always have a way to duck down behind it. If friendly infantry are getting overun then its time to displace to a new area...and if you start racking up kills you can be sure someone is now out to get ya. Stationary = impending death