Select the gun as if ready to shoot. Pause game play, exit the menu, then press B, A. after returning to the game screen. The pointer will change from a crosshair to a hand.
After getting the first gun and killing the Troll/running away (wuss) go to the cemetery located between Jake's regular bar and the club.
There are 8 ghouls to kill, killing 4 gives 1 point of karma and exiting the area will cause the ghouls to reset when you return, increasing your gun skill makes it easier to hit them and makes you do more damage with each hit.
Press Select + Start + L + R during game play.
First, go to the Club and ask the bartender for some Iced Tea, but do not drink it. Go to the angry patron and give him the tea. Talk to him and he will mention 'Grinder'. Ask him about Grinder to learn 'Lone Star'. Go to the fencer, who sells grenades, and ask about 'Lone Star'. You can now get the badge for 150.