I personally found this easier to do on 2Fort, but other people might have found it easier on different maps. Obviously, you need to be scout and you need to be in a capture the flag server. You have to get there and back without firing a shot, so you need to be careful, and you need to be quick. Ensure you use cover to check where enemies are before you go sprinting out into a possible ambush. When you have the intelligence, run. Run as fast as you can. Most enemies you can outrun and also dodge attacks by moving left and right as you run. The moment you're in your base, you should be good, but don't let up until you've got the intelligence.