Ugh, I hate answering this.
On my first way through, I just play the game.
What ever seems like a good idea at the time, I do.
Let's use Fallout 3 as an example.
I laid the smack down on Butch, I hated him.
I shot the Overseer, I hated his pompous self (That's right, I heard that comment about me being a snot-nosed brat!)
I saved Megaton, but Lucas got shot. (Took Lucas' Gun)
I went hard-core optional for Moria. (Didn't know about the perk either)
Jacked Moriatry's Terminal for the info.
Killed Silver, took her money.
Saved Harold (always liked him, didn't feel he should die, got some nice armor)
Saved Reilly's Rangers, got awesome armor.
Was nice to ghouls, got nice stuff.
Betrayed Crowley, on accident, I wanted to see where the keys led.
Killed Tenpenny after I let Roy in.
Killed Roy.
Killed everyone in hte Tower EXCEPT Dashwood.
Saved Fawkes, got him later after Raven Rock.
It goes on and on. But, I tried to serve myself in Fallout 3.
What should have been evil choices netted me "Better than Jesus" karma in the end.
I didn't shoot Three dog either.