Barry is correct, the way to prevent is by communicating with the people most at risk.
Completely hypothetical, but if you come from an Asian community in a poor area of an inner city, you're unemployed, you have very few support networks and your future looks bleak. A man then comes along, puts his arm around you and preaches to you about how Islam can improve your life. You get sucked in and suddenly the preacher becomes more radical, you believe in this person more and more and bang hey presto, you're radicalised.
I think in this country we do integration a lot better than France for example but obviously it's a battle that may never be completely won.