I dont tend to choose outright, just do whatever amuses me most at the time, so using fallout 3, was too tempting not to blow up megaton, an evil decision, yet later i talked the people in ten penny tower to let the ghouls stay with them, a "good" decision apparently, that game had a lot of grey lines. So by the end of that game I was still fairly neutral/slightly evil
Mass effect is another good example, too tempting not to punch a news reporter or shove a guy out of an appartment window, but I also couldnt bring myself to have garrus kill that pathetic guy he had been tracking, instead used my fem shepard's "charms" to show him mercy
Oh and in dragon age, was a huge jerk in conversation trees, just because some of them were too funny not to, but my in game actions were normally good... so yeah, in general, just whatever I feel like at the time.