First off, beat the game on Easy and Normal first. This way, you get more skill points for your character. after you've done that, just play through the game. If you're decent you can beat it on Hard in 3 1/2 to 4 hours. You WILL die a moderate amount of times. This is where this becomes like COD4's Deep and Hard achievement, take cover and keep a long and short ranged weapon at hand. My favorite loadout is the Henry rifle because of its incredible adaptability of range, and the Pepperbox pistol because of its strength. In addition, keep LOTS of grenades handy, as they will prove both useful and lifesaving especially in the last 3 missions of the game.