Intro Scene
Shoot to skip your meeting with the prospector. Shoot the two bad guys to save the prospector and move on to the scene selection. It does not matter which order you do the areas in, except that selecting sheriff before saloon forces you to waste time backtracking.
Corral
Shoot the two guys that look at you. There is a third guy you must shoot in the corral window after the first two, and the visual indicator is super small, so just spam it.
Corral Shootout
Shoot the people as they appear. Their pattern is completely random, but ends with the guy in the top right falling down. Shoot him when he draws his gun a second time to finish the barn. Going back to town, a man on a horse approaches you. Shoot the horse to finish the area.
Saloon
You cannot shoot the guy on the roof the first time. Wait until the camera is still, then shoot the roof guy. Do not shoot the woman or the bartender or it's a game over. Wait until Jacko draws his gun on the bartender, then shoot him (left of One-Eyed-Jack). Shoot One-Eyed-Jack when he draws his gun, then his henchmen from left to right. If the bartender dies, it's game over.
Sheriff's Office
Same with saloon, wait till the camera is still then shoot the guy that rounds the corner. Enter the office and shoot the guy in the window. When outside, the sheriff will shoot two people then die. Shoot the last guy to finish the area. You cannot save the sheriff.
Bank
Do not shoot the kid running out. Shoot red guy and his buddy. Enter the bank, and proceed to take everyone out. There is a hostage that is brought up in the middle hind desk. Do not shoot him or game over. The hostage pattern is random, appearing 1-2 times. Hope you get a 1 hostage pattern. Remember what the bank kid tells you once you finish this area.
Prospector
Shoot the fuse to save the prospector.
Mine
There are 3 possible patterns (that I know). You have to either shoot out the gold pan, the mineshaft sign, or the pitchfork. Shoot out the respective item and then the lantern on the box. Shoot all 3 bottles the prospector throws up. A trick is to keep your crosshair in the middle top area, since you can hit it no matter which direction it is thrown from. You then get to look at the map.
Map
The map is randomly generated each run. There are 2 kinds of maps. Left map and right map, referring to the X location. Left map saves around 30 - 40 seconds, since it only has 2 shootouts instead of 3.
Hideout
Take the right path depending on the map. A mistake is a game over. Each direction leads to a shootout. Approach the hideout from the opposite side bank boy told you to avoid. Shoot the two guys, then when the camera pans over, shoot the guy behind the barrel. Shoot out the smokestack to lure everyone out. 4 people will run out, shoot them all, then the mayor runs out. Don't shoot him or it's game over. Inside, you'll see another person in the smoke. Shoot him and you'll head back to town.
There is a hotel 'wack-a-mole' style shootout here. Hitboxes are generous, so just shooting the window they are in is usually enough. Finish this to get to Mad Dog.
Mad Doug
Shoot his hand, then again when he draws his second gun. End the run when he is shot again.