This is exactly what you need to do to get through each mission (not including the bonus mission): Training: shoot the white targets when they pop up. don't worry about time - they won't go back down until you shoot them. Mission 1: shoot the guy who sticks his head up out of the mortar pit. Mission 2: shoot the guy leaning against the tree, then shoot the guy in the tower. Mission 3: shoot the guy in the tower, then the guy on the log, then the guy leaning against the tent. Mission 4: shoot the men standing in the open hatches of the tanks when they come past. Mission 5: fairly simple - shoot the guy on the machine gun. Don't shoot 2 close guys because they are your troops. Mission 6: look for any suspicious dark circles in the building - he is in a different place each time. If he starts taking shots at you, look for where the muzzle flash is coming from. Mission 7: you NEED a semi-auto for this - I recommend the sig 550. First, shoot the guy who walks across the upstairs window. Then shoot the interrogator on the right, and QUICKLY shoot the one on the left. Mission 8: keep your crosshairs on the gap between 2 carriages and shoot the guy in the hat when he walks past. Don't shoot his guards. Mission 9: listen to the spotter, but when he tells you to shoot the gunner below the north building, wait for the APC to go past, then carry on shooting. Mission 10: shoot the little radio/generator and a guard will appear. Shoot this guard in the LEG. When the bunker opens, shoot the power box inside. Mission 11: this is pure skill - you either have it or you don't. Just shoot the two motorcyclists as they go past.
Tip: when you get the best scope, go back and do the training and you can get £8500 easily.
For level 7 you can also shoot the guy who walks past, then shoot the lights above them and the squad will do the rest. By the way can someone help me with level 9 more thoroughly.
I figured out a really easy way to beat the game. If you start on the bonus level, and let the car drive by, you'll fail and get to keep the really nice rifle. Then, you will be able complete the training mission achievements with ease, and earn enough money to purchase anything. Move through the levels until you reach the eleventh, before which you should complete the bonus mission and buy the gun. Then complete the final level.
@BitterComedy: You got that one Right, dude! it works! ;D @theperson1996 on Level 11: Pure Skill, huh.. Well, not really~ you can use the diazepam to ease your sniping.
I still don't understand how to beat the Bonus Mission.. since the car just moves fast. I guess this Bonus Mission would use a Pure-Skill.