For one on one defending, the thing I find that works best is once they get the ball, sort of backtrack at the same pace as the attacker once they have the ball. So say an attacker has just received the ball, and they turn and face you, but have yet to try and get past you. Keep a distance, and if they bring it slowly towards you (say before then running quickly to get past you), go slowly backwards with them whilst still facing them to maintain a similar sort of distance between the two of you. It helps because as well as keeping distance, you're travelling at a similar speed, so if they try and knock it past you you'll be able to accelerate at a similar level to them too. Full backs like Ashley cole who constantly get attacked by wingers do this, so they dont get run past (you could try watching some of his vids).
Edit - basically what the guy above said with the show one side and shimmy bit.
For attacking, what you need to use is what I call the 'force'. Basically, you get the ball, face the attacker, and run. When you get close enough for them to tackle you, shimmy your body like messi does away from them, run to it and continue like a hero. . Believe in yourself. Messi started out like you, and he did it. You can too. If that doesn't work, you can try the easier three stepovers before running method, it's easier and confuses defenders, but is not as glorious as the force. Finally, this para's not serious. It's hard to attack without good ball control and being able to make a good few touches in tandem when running, but the best thing I can give you is Antonio Valencia / Henry style knock and run. It's not just knock run though, you need to go fairly fast with the ball before knocking it, as you'll need to have enough pre speed to beat the defender, and you only knock it when the defender tries to tackle it, so that when you run he'll have slowed down. If he does the defending I mentioned above, this won't work, and you'll probs lose the ball and look a bit stupid.