The Role Of The Central Defender
READING THE GAME AND BREAKING DOWN ATTACKS
As a center back it's important that you have the ability to read the game and break down attacks. You cannot be a good defender without being able to read the game. why, because you see everything. As a center back you have the chance to see and anticipate what might happen. All the best defenders have this attribute. e.g. John Terry. This skill is hard to develop it mostly comes with experience, but the more games you watch the better you will understand the game, and be able to understand the game.
HEADING
No doubt playing at center back you will be doing your fair share of contesting headers. Weather it being crosses or long balls to striker's you need to be dominant in the air. The one advantage a center back has over the striker is that your just trying to win the ball, the striker has to try and keep it. One trick to use to win an aerial battle is to jump first, but not o early. As a center back you will generally be behind the striker, so if you jump first he can't jump through you. Remember to keep your hands down, and not to give away cheap fouls. Watch center backs like Rio Ferdinand they always win their aerial contests, and they are generally in the air first.
CLEARING
Playing at center back you are the last line of defense so you cannot at any price loose the ball cheaply. e.g. Trying to dribble the ball out of your 18 yard box. Depending on the situation you always want to try and keep the ball where possible. But if you are under the pump in your own penalty area by all means knock the ball clear. If you have the chance when clearing to aim for the half way side line as it allows you to regroup and push up the park. If you want to be recognized as a top defender you to learn to play out from the back. To do this you have to have a good sense of awareness. Knowing where your team mates are before you get the ball.
This comes practice from football training (soccer training) learning to be aware in small sided games, this will naturally progress into normal regular games.
TACKLING
For tackling i recommend that you read the topic on tackling at tackling
COMMUNICATION AND SUPPORT
As a center back you have to be dominant on the pitch both physically and mentally. As you can see the whole pitch as once it's crucial for your team that you communicate during the match. This can be as simple as: turn, man on (telling your team mate he has pressure), telling a team mate where he can pass the ball, directing players around defensively (who to mark). The modern center back has to be available to get the ball as often as possible, look at Barcelona F.C. they always have the lion's share of possession because they have center backs that are good players with the ball and support their team mates at every opportunity. Being able able to use the ball as a center back gives you personally another tick as a player, because it gives your team an extra dimension another passing option.
MARKING
Marking is a major part to a center backs game. Being close to strikers but not to close at the wrong times. Players get better marking the more they play. It's difficult to explain marking as there are different styles to contend with. Man marking is obvious you pick up the striker that is closest to you. And then theres zonal marking where you have an area on the pitch that is yours and any opposition player that comes into your area then that player takes your priority. But when marking in general you must stay goal side, unless you have clear opportunity to win the ball. How close you mark an opponent really depends on that specific player e.g. A fast player, you might want give a few yards as if you get to close they might turn, run past you connecting up with a through ball. Skillful players get to close and they will roll of you, to far away and they will turn and try to dazzle you. A method that works is as a striker drops short to get the ball, pressure him, just before contact let him know your there by either a slight nudge, hand in the back (it's important not to push and be careful so he referee doesn't call a foul against you). Then giving the striker 1-2 yards of space to see what he is going to do. There no doubting that you have to put pressure on the striker but how much comes with experience and knowledge of that player.
Overall center defenders player a critical role in any team. They say strikers win games and defenders win championship, that is pretty close to the truth as the team that wins the trophy at the end of the year usually has a good defensive record. For players wishing to improve you must watch the best players in your position and mimic what they do. Best of luck.