In interrogation as it exists right now it's most important to 1) have high interrogation skill and 2) have stockholm syndrome happen. Get the first by training your interrogator(s) up on weak conservatives such as janitors, extra sleepers is never a bad thing. To get the second you need to give your good cop interrogator time with the conservative treating him relatively gentle i.e. no beating, no starvation or thirsting more then 2 days.
To see an exact method read the spoiler and take all the fun out of figuring the system out for yourself, completely unbalancing the game:
First day of the game, my founder goes out and steals some stuff. Second day he or she sells it and buys a weapon (spray can counts!) to count as "armed" for kidnapping. Day three is seduce a janitor and kidnap him/her if wisdom isn't much higher then cha (starting out easy.)
For first day of interrogation, no food, no water no sleep, no beating, no drugs, no props final destination! (http://www.youtube.com/watch?v=O-7gmds2njg). Day two is repeat. On day three, let the conservative sleep, eat and drink but follow it up with two days without these again. Go back and forth in this fashion and it shouldn't be too hard.
Use this same method on all conservatives, kidnap, starve/thirst/sleepless two days on one day off repeat. Once you get your skill trained up, you can take on some conservatives who matter but who don't have any of the social skills (business, science, religion, gangsterism.) I.e. you can take on radio hosts but not business people or CEO's. Once your skill is high you can take on anyone without the interrogation skill themselves. In order to take on someone with high interrogation skill, i.e. agents. You need maxed out interrogation or patience.
The alternative to the "good cop" method outlined above is the "good cop-bad cop" method. Beat, starve, drug, etc. the victim for a couple days with a low-heart thug, then switch to a sweet-talker and confuse them with your kindness. If the sweet talker is good enough, they can take both roles, but it's often easier to break them with a different person. This is good for punching through large blocks of Wisdom, but has the downside of ruining the Health and Heart of the victim, unlike the pure "good cop" method.