To unlock this achievement, you need to complete any 8 of the level trials that are available while playing on the Operative difficulty. A list of 8 level trials on the Operative difficulty can be found below;
Goldfinger - Auric Enterprises - Accuracy: Keep your hit ratio above 90%.
Goldfinger - Fort Knoxx - Accuracy: Keep your hit ratio above 80%.
O.H.M.S.S. - Alpine Valley - Accuracy: Keep your hit ratio above 15%.
O.H.M.S.S. - Blofeld's Lair - Time: Complete the level within 25 minutes and 30 seconds.
License to Kill - Refinery - Time: Complete the level within 20 minutes.
Die Another Day - Ice Hotel - Time: Complete the level within 24 minutes.
Moonraker - Spaceport - Stealth: From the start of the level, up to meeting Jaws.
Moonraker - Space Station - Elimination: Make 40 Eliminations with the Moonraker Laser.
You will know when you have completed one of these trials, as it will appear in the lower left corner of the screen upon completion. You can also see which ones you have completed by going to 'Mission Select' form the main menu, and as you highlight a mission, you will see on the right hand side of the screen, a list of the trials underneath each missions details with a box next to each. If the box has a tick in it, then you have completed it.