It is not easy to do. Getting good at Vipassana meditation is like staring akrasia in the face and trying to conquer it. I usually end up dwelling on some recursive bad thought and get too anxious to keep going for much longer than 10 minutes. I think this is a pretty common thing for attempted practitioners of Vipassana meditation... it's tough to acknowledge that nothing really matters and that you can just sit and watch your breath for a while.

One thing I find helps is a cross between GTD & vipassana: keeping a notepad nearby.

I like Mindfulness in Plain English, personally.