Hmmm, after thinking about this, I think my philosophy when playing can be boiled down to "Explore the unknown."
Playing New Vegas for the first time and encountering the Legion was crazy. Then I learned you can play as them and I immediately started over and made a "made for the legion" character. I was too fascinated by the ability to play as that side, imagining what lay on it's side of the fence mechanically and writing wise. Most of the time I try to get in a characters head. Why would they be doing the things they're doing? Associating with who they do? Is it straight forward? A contradiction, that even they themselves are uncomfortable with, but realize is a neccesary action?
On the more 'game-y' side of things, in Borderlands 2 I was struck one day while looking at Salvadors trees with the idea for a Hyperion weapon based Rampage build. Those weapons get more accurate as you fire and that tree is designed to let you keep firing longer and longer, so I thought "I could have two shotguns as accurate as sniper rifles" and boom, I was on my way. It's probably not the most optimal build ever, but optimal very rarely filters into my decisions when making characters, unless I am in fact designing them to be as pointed as possible.
Once upon a time I think all I ever did in games was power play. I'd always sort out which was the "best" weapon/strategy/armor what have you, and I had a clear opinion on what was good and what wasn't. Good example being Fallout 3. Shotgun w combat armor and an AR for mirelurks, maybe an explosive weapon for fun/sticky situations, anything else I felt was a waste of time. It actually bewildered me why anyone would wear anything but the absolute best stuff.
I'm personally glad I've moved beyond that. It's allowed me to get a lot more (and more replay value) out of my games.