Well, if you want to work on Wing and CM traits, here's some tips.
A central midfield should be strong on the attack, as well as on the defense. You need to have good vision and passing skills, as well as a decent shot (depending on how far forward you intend on pushing up). You also have to be in tip top shape to play CM effectively IMO, as you're going to be going back and forth. Being strong and having a physical presence is an added bonus (though not always necessary, look at Iniesta and Xavi, that being said, they try to avoid physical battles as much as possible).
Vision is something you can't really practice on your own, the only real way to practice it is to actually play in games. Any game experience you can get will be valuable. Watching professional games helps slightly, so any time you can, try to watch games on TV, etc.
Passing, like vision, is easier to train with game experience, but you CAN practice passing by yourself. Pass to an empty net, envision where you intend on passing and make it happen. You can pass to obstacles, or just have a pal go to the fields with you to pass around as well.
Shooting: As a CM, most shots are going to come from the 18 or outside of it, therefore having a powerful instep drive and an accurate finesse is a good thing to possess. I'd imagine you have a field somewhere, or even a wall. Practice shooting at it, if you're having trouble with instep drives, here's a guide on mastering it.
Fitness: You're going to have to be able to do a LOT of running in the midfield, so you need to be in shape. Go out and run several miles a couple times a week (vaguely) until you are in better shape, then kick it up a notch (maybe run several miles several times a week). Now for actual quickness, training is a bit more complicated. Have a look at this: http://expertfootball.com/training/speed_training.php
As a winger, you have to have great control (being to go past the opposition), good vision and passing, good crossing, speed, and a good shot.
We've already discussed vision and passing and shots on goal, let's talk about control. I'm not sure what level you play at, so I really don't want to have to tell you things like "dribble around cones" etc. Control can be trained in many ways, juggling, kicking against a wall to practice trapping, etc. Get as many touches on the ball, dribble as fast as you can, practice going around obstacles. On a rainy day, dribble around inside to really practice your close control. All those things help.
Crossing is a bit difficult to train, best to do it with friends at the fields IMO. Practice going down the field and getting the ball to your targets inside the box.
Last but not least, here's a good page that explains what each position's roles are: http://expertfootball.com/coaching/positions.php