There are two locations you need to know:
1) Hotels & Marina District (In the top corner next to the celeb. activity and the burger shop)
-Level 3 Completed: Ronin Notoriety reduces 5% faster
-Level 6 Completed: Ronin Notoriety reduces 15% faster
2) Airport District (Next to the hangar where you can store planes; AKA your "crib")
-Level 3 Completed: XS-2 Ultimax Shotgun at Crib
-Level 6 Completed: Unlimited Shotgun Ammo
Once you complete both activities, the achievement will unlock. Drug Trafficking is when you must protect a drug dealer driving around town, delivering drugs to people. You are in the passenger seat, and you can get out and follow the dealer. If your car blows up, get a new one. Eventually, the gang notoriety will get higher, and drug deals will become longer. And, the customer will sometimes run off, forcing you to kill them.