Here's an effective and foolproof way to score infinite Renegade points. When you get to the part of the game where Lorik Quinn is going to testify against Anoleis, speak to Lorik Quinn and convince him to testify. This will give you twenty-five Renegade poionts. Then, walk away from him, return to him, and ask him something unrelated to the case. You'll then be given the option to "Answer another question", at which point you'll be able to convince him to testify again, for another twenty-five Renegade points. You can repeat this indefinitely until you score the amount of points you want.

An addition by orp08:

You can get Paragon points using the method as well, just as easily as you can get Renegade points. Just select the blue-colored (Paragon) option instead of the red-colored (Renegade) option, and as before, you can do this over and over again as desired.