Don't CampThis one should be a no-brainer, but many people feel as though camping allows them to draw enemies to them and get the upper hand. Not only is this incredibly annoying for everyone else, it's also one of the worst tactics anyone could use in Call of Duty. Camping may be nice to get you a few kills, but I can guarantee the longer you stay in one spot, the greater your chances of being ambushed and killed. If you're going to camp, move after every 1-2 kills. This way, the enemy doesn't have time to hunt you down and exact his revenge.
AimThis one is a two-parter. Increasing your aim coincides with your settings. You need to mess with your aim sensitivity until you find a level that is comfortable for you. It should be slow enough that you're not always overshooting your targets, but fast enough that you can turn around fairly quickly to check behind you. This is probably one of the harder tips, as it requires a lot of trial and error, but when this is done properly, it can be the difference between winning and losing. Once those settings are in place, aiming is the next important step. Make sure that you aren't always firing from the hip. I typically begin firing before bringing up the sights, but I make sure that I am bringing those sights up almost immediately after seeing my target. Firing from the hip decreases your accuracy greatly, and while you are missing, you're giving the enemy time to bring up his sights and take you out. It will take time to better your aim, but it's not something that you necessarily have to think about to get better. Remember the old saying, "practice makes perfect".
Calm DownThis is an important step as well. If you get too worked up over the game, it can really make it harder to play. Try to sit down, relax, and breathe. The more calm you get, the more you can focus on your surroundings within the game. Just keep in mind that this is a video game and you can't die in real life by getting shot in the game.
Know the Maps!I cannot express this enough. This is an extremely important step toward better kill/death ratios. This goes hand in hand with camping. If you spend your time camping, you will never be able to fully explore and truly "know" every map. Think of each map like a city. Knowing the map allows you to know where the busiest areas are and where the best cover is located. This is a long process, and can take days or even weeks to fully understand how each map works. The more you know about the map, the better you can perform. Many of the greats in Call of Duty get that way because they know the ins and outs of every map, and how to maneuver through the low traffic areas to get a good vantage point. It's imperative that you take your time here, and you will be surprised by how well you play just following this step.
Use CoverWhen I first began playing Call of Duty, I was such an easy target. When I joined the military, I thought to take my tactical knowledge and apply it to my gameplay. I noticed that just by using cover, I was able to remain undetected much longer, and in many cases, it allowed me to get the jump on my enemy. The best thing you can do when moving through the map is to move from cover to cover. This is where sprint comes in very handy. Always try to stick to routes that allow plenty of cover, and don't run into open areas unless you feel comfortable enough with your ability. If you are in the open most of the time, you had better hope that you are the best player on the server, because you're making yourself an easy target.
Use Sprint SparinglyThe only reason behind this is the fact that when you are always sprinting, you're slowing down your ability to react when you see an enemy. Sprint is a wonderful tool when travelling from cover to cover, but if you sprint all of the time, you're making it harder on yourself to kill the enemy before they kill you. When not using cover, try moving with your sights up so that you're already set to pull the trigger. When travelling around corners, keep your sights near the corner and "pie the corner", as we called it in the army. What this means is that you should take a wide angle around the corner instead of hugging the wall, and make sure that you are watching the corner in case there is an enemy.
I hope that you've found my tips helpful. If you have any questions, feel free to ask and I will see what I can do about finding an answer. Don't forget to comment, and if you like what you see on my blog, go ahead and subscribe so you can be updated every time I make a new post here.