There're really only two viable approaches:
1. Go in heavy and stay long, nation-building, the Long War, all of that stuff. It works, but it takes an enduring and unwavering commitment (Which the US government has proven to be exceptionally disinclined to invest in counterinsurgent conflicts since the Philippine Insurrection).
2. Say "**** it" and go home.
Anything else is just a longer, more casualty-producing, and much more expensive version of #2.