I play either right back or in midfield and my weakest points are just my heading and tackling. I never win headers as i am usually shorter than the people im marking plus im not too good at heading in the first place. Also i seem to let people run past me at times without putting a foot in i usually prefer to jockey and then snatch the ball off my opposition at the right time. How can i improve my heading and just overall tackling?
If your not tall enough, compromise - train your explosive power/vertical leap. Weights and plyo's my man.
For heading in general? If you can find a training partner, get him to whip long balls towards you, and ou just practice clearing them away with your head. Once you've got it down pat, kidnap another training partner and et him to act as the attacker in the situation. Just get him to pressure for the ball at first, not leap up and contest, this should be the final stage of the drill.
Positioning is also important for winning headers, but I won't get in to it right now, it late for me. It will mostly come from experience anyway.
For tackling, your going to have to build your hunger for the ball - your aggression. Some, well probably most people sent born with this natural aggression for tackling, but it can be improved on my motivating yourself more before the game, intensifying a hate for the opposition. I'm not an overly aggressive tackler, bu I know I should be, so I just do it, I go in hard because I need to. If you get to see Arsenal play recently keep an eye on youg Frimpong, he's out there to kill people, I know it. It's brilliant.