My personal interrogation strategy is this:
1. -DO NOT- interrogate -OR- beat them with your main interrogator, for the first few days. During this time, never let the captive see your face. OR, you can beat them, but you need to not have your main interrogator involved this early in the process. The captive -will- remember -anyone- who they see treating them roughly -- if you starve them, then send in your guy to talk, and your guy doesn't give him food, he's going to hate your guy because he'll see your guy as the one responsible for starving him. He's not going to be amenable to your guy's point of view at all -- trying to argue with him then, he'll just lose it further. By avoiding both verbal interrogation and beatings, or by using throwaway interrogators when attacking them, you can ensure the target never associates the face of your best person with "evil". At the moment the system is pretty harsh about this, much more than it should be, and it's not very transparent -- you don't get any feedback that shows that the person associates your interrogator with the rough treatment they got. But as long as you follow this rule, you can experiment with being rough, and use this time to crush his wisdom.
2. When the target's wisdom hits 1, turn everything off all at once, and make this day the "grand entrance" for your lead interrogator. The good cop has arrived to save the day, with a clean slate record! From now on, always be nice with them. Drug use is okay, but risky. Try sticking to nice talks. If you're feeling lucky, you can even untie them. Letting them roam freely in a back room will make them feel better about whoever you have questioning them. Watch out though -- keeping them tied up keeps them from causing trouble. If they escape, better abandon your safehouse quick, because they'll tell the police EXACTLY where you are!
3. Profit!