There are many ways to improve your Kill Death Ratio I will focus on a few. Having a high KDR is all about ones pride and skill. Here a some tips that will improve your KDR.
(1) Understanding the map
Knowing the map plays a huge part in your KDR if you know where to go at the right times you can capitalize on kills fast. Some routes and angles are a guaranteed kill for you if you play your cards right. You need to spend some time and free unturned skins
familiarize yourself with buildings, corners, blind spots, line of sight, little areas on the map where you can look through or behind cracks in the walls or doors even little spots through bushes. Once you understand a map and how long it takes for people to get from one spot to another you can position your self in ways that will make you seem like a god and or mind reader. That's the key right there. For an example, As you run through the map, There will be certain areas you'll look for (typical where you normally get killed from) once you do this enough it will become second nature for you, There are many times where i have loaded into a server and simply because i know where people shoot from.. I'd just pop off a few shots randomly and get kills.
Sometimes I even jump around a corner and pre fire and there will be 2-3 people sitting there camping or something. There are also times when I bait the enemy.. If everything is quite I'll fire a shot or 2 then quickly aim at the window or depending where I am a door way or corner and someone will poke their head out looking to kill me but by the time they aim I'm already firing at them.
(2) Picking the right guns
There are a few ways to look at this. Some players say that there are certain guns you use in certain maps then you have the players that are good with only a hand full of guns My suggestion is if you trying to play a serious game then use what your good with simple as that. I'm good with the scout in CSS any map any amount of players it doesn't matter im a beast! Close range or long range. Same goes for the Ak47 I can snipe with that baby in any game! COD MW COD MW2 and CSS. If you want to practice with other weapons go for it. It's always good to be versatile but if you want to walk out of the round with a HIGH KDR stick to what you know.
(3) Know your Limits
If you are a sniper don't try to run and gun with a semi auto.. If sniping isn't your cup of tea don't pick it up. If you are not good at facing multiple enemies it might be a good idea for you to play slower and pick choke points that you can control on the map. Now I'm not saying outright camp (although that is good idea) I'm just saying make sue you have a few spots on the map that you can will a shoot out in 70% of the time. This will give you a huge advantage in any FPS game
(4): Play cheap (no cheat)
SPAWN CAMP ANY CHANCE YOU HAVE.. Why? Well if you are like me you like to upset people lol.. Seriously do whatever it takes besides cheating to get your kills.. Nade spam, camp, camp spawns etc
Some of my favorite games
Call Of Duty 2
Call Of Duty 4
Modern Warfare 2
Counter Strike Source
MOH Limited Edition
(4) Great Headphones
Let's face it if you can't hear what's going on in game you're not going to survive. You need a great set of headphones that will allow you to hear where the enemy is at all times even when they are walking stealth mode. Ever wonder how someone knew when and where to pop out and shoot? No it's not because they were cheating it's because they can hear you! or they had someone on ts/ventrilio ghosting your position. I always attach when I hear the enemy switching weapons or reloading without good headphones I'd be lost!
Have fun guys and gals.