Press Select + Start + L + R during game play.

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.

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.