First, I generally don't think of the renegade actions as being Evil. They are, generally speaking at any rate, a way to solve a problem, often in the simplest and most efficient manner. Sure, those solutions might be a bit dickish but I hardly think that qualifies as being evil.
And, for my part, I tend to choose the option that makes the most sense at the moment without regard to if the option is paragon or renegade. If I need to sabatoge a gunship and the option comes up to stab a guy in the back with a power tool, I'll take that option. Or, if some guy is braging about how they've got me in an ambush and I can choose to snap his neck and drop an exploding crate on a bunch of his cohorts, I'll take that as well. By the end of the game this left me being entirely paragon and nearly 50% renegade.