A good spot would be a place where he has got to run in the open to get you. If possible, keep his flag station close because you're guaranteed he'll be coming your way. Remember that he is close to his flag station so he is going to be sloppy and in a hurry. Sucker him out and let him think that he has the advantage on you and then come and blast him. Robbo falls for this the best.
Some flag carriers come back the same way they went up the field, which is usually down a wire.
If you see the other team doing this you have got to know if you can beat them to the station. If you are running down the opposite wire and both of you see each other across the field you have got to go. Haul ass unless you don't think that your overgrown, top heavy chest and bald head can't make it to the station before I do. Those are most of the situations that you may run into, but there are still a few more. The other team may get behind you, grab the flag and try to run it back.