The following is a walkthrough of the Snail Trail mission in Grand Theft Auto: San Andreas.
Mission Brief
Frank Tenpenny and Eddie Pulaski wants Carl Johnson to kill a reporter and a journalist who's onto them.
Walkthrough
First of all, go pick up the sniper rifle Tenpenny hid in the construction site beside the garage. Once it has been collected, head for Cranberry Station. Once there, it is most likely that the reporter has already boarded the train, so just follow the train to Market Station in Los Santos, but be careful of trains on the opposite track. Once it has arrived in Market Station, the journalist will exit the train, and a Spook-O-Meter will appear. Be careful not to go too near to him, as this would freak him out and the mission would fail. Be careful also not too be too far away, as this would also lead to a mission failure. As he goes up to the surface, he will ride a cab. Follow the cab and remember to keep your distance. When the journalist has reached the end of the pier in Santa Maria Beach, he will meet the reporter. Kill them both to complete the mission. You only have to kill one with the sniper rifle; it might be easier to just get closer and use another weapon (besides the sniper rifle) to finish off the other target, because he will run like a madman once the other has been killed - making it somewhat difficult to pick him off with a sniper.
Alternative: You haven't to follow the train all the way to L.S. along the railway track. You may use the streets as well which is much quicker and more confortable. In L.S. wait south of Market Station for the trains arrival..