I try to buy into the worlds premise and just go with the flow the first time.
If the game is not that immersive I just end up playing the goody-goody two shoes, because years of gaming has conditioned me to that being the optimal path which gives me maximum character interactions which is what I want.
If the game is good and immersive some kind of character emerge itself for me in the early parts and that is usually the character I stick with. Those characters tend to be darker, because I have always enjoyed villains in fiction a little more than heroes, they are so much more emotional and passionate and I enjoy passion. I really do. I am a sap, though and will always try to guide my MC to the best possible outcome for them. (Though, they may not always deserve it.)