Get To Know the Weapons, and the Maps.
Your Weapon Is Your Partner - Choose Wisely
As stated earlier, choosing the right weapon can have a drastic impact on your results, and this varies quite a bit from game to game. In the next example, I'll refer to a couple of weapons in Rainbow Six 3, a tactical shooter available on PC and most consoles. Many people recommend using the G3A3 rifle for use in RS3, and for good reason, it is the most powerful rifle, bullet for bullet, in the game.
However, it also has some major drawbacks. First off, it only holds 21 rounds per clip, where other weapons will hold over 30. It also has a significant recoil, enough to make you miss more often than not. For these two reasons, I actually prefer the TAR-21, which has a 31 round clip and much less of a recoil, but based on the way the game ranks the weapons, this would not be your first pick. While it may not have the 3.5x scope, it does have a 2.0x scope, and I can get double the kills with this gun by using the methods described in this article.
Know and Use the Maps to Your Advantage
Knowing the maps extremely well will only be helpful in multi player games, but knowing the terrain on any given map will serve more than one purpose. In single player and multi player games using the environment within the map to take cover and avoid enemy fire will be crucial to staying alive. Use every outlet the map and environment give you, ducking behind barrels, hiding behind walls, whatever it takes to stay safe.
One key tip during times when taking heavy fire from enemies is to stay behind cover until you hear them reload, then come out from your little safe haven and blast them to pieces while they are reloading.
Practice Makes Perfect
Practice as Often as Possible and Reap the Rewards
Sure its an old cliche, but it holds true in the case of Video Game Strategies. Of course your first go around with a shooter game is going to be a mess, and you'll likely find yourself dead more times than alive, but as you become more familiar with the game you will only get better and better. As time goes on, building up your skills in one particular shooter will help you across all games in the shooter genre, but they all have their unique qualities, so don't expect to be a master at Halo 2 just because you are great at Rainbow Six 3.
It takes time to become one of the best, and most of us, myself included, just do not have the time to be the absolute best we can be. If you look at the leader boards on some of the online gaming systems, you'll see that the top ranked players for any particular game, basically play that game constantly. Sure, they're great at that game, but you would be too if that was all you ever played. The bottom line is, be what you can be, make the best of what you have to work with, and have fun along the way.