Three Things Every Good Player Must Do

1. Last Hit

Last hitting is important because it gives you gold for the minion kill. In addition, you receive experience for the kill.

2. Counterpick
Counterpicking is extremely important, though more so at higher levels, it is still very important.
For example, a good counterpick to Akali is Renekton.

3. Have a jungler.
A jungler is extremely important and can save the day, make sure your team has a jungler or if not, cover for it yourself!