The short answer
Swapping saturated fat for unsaturated fat, adding soluble fiber, and plant sterols. Together they add up.
Saturated fat (butter, fatty meat, cheese, coconut oil) swapped for olive oil, nuts and fish: about 8 to 10% lower LDL.
Soluble fiber, 5 to 10 g a day from oats, beans, lentils or psyllium: about 3 to 5%. Plant sterols, 2 g a day: about 6 to 15%. Losing about 10 pounds: about 5%.
Source: NCEP ATP III, Circulation 2002.