How could you RP a Enforcer/Detective

Get some friends to join you. It's always more fun with a friend. Make sure you can trust them with your secrets and master plan. If you have a group, try creating a few missions and assigning each "agent" to each mission.
Create an "assignment". Choose a target, find a lead, and create a master plan (with a back up, of course).
Make sure you're prepared for your mission. Your pen should be fully inked, your flashlight should have a full battery, your tape recorder should have tape in it, etc. Go on a practice run before the mission, just to make sure everything will go as planned. If you have enough friends with you, you can even make a Detective training.
Create a secret base. This can be as complex as a hidden room behind a bookshelf or as simple as a mouse hole, a BIG mouse hole.