Be responsible for your own learning
Sure you have teachers, reading materials, and websites to help you with your English, but who is really responsible for making sure you learn English well? Nobody but you. Make sure you are the one who is taking charge of your own learning. There is a good article about the subject on the 5 Minute English website. It's at www.5minuteenglish.com/articles. Check it out.
Immerse yourself in English as much as possible
Immerse means to be surrounded by something. If you are immersed in English, it is all around you. Of course this isn't always possible, but you can do some things to surround yourself in English from time to time.
Listen to the radio in English. If there are no English radio stations where you live, listen to one on the internet.
Watch TV and movies in English. If you have English channels on your TV, watch them. If they have subtitles (the words written in your language) underneath the picture, see if they can be turned off. Some people even tape paper across the bottom of the screen so they can't see the words. Most DVD's are great because you can choose the language you want to hear.
Speak English to your friends. Get a conversation buddy (friend) and speak in English as much as possible. If it is a person whose native language is the same as your own, you may feel silly speaking in English at first. But don't worry. Continue to do it and it will become more natural to you. Finding friends whose native language is English is even better. Ask your friend to correct you when needed.
Study or travel to an English-speaking country. Of course the best way to immerse yourself in the English language is to live in an all English environment. You'll find yourself surrounded with the language everywhere you turn. It can be a more difficult and expensive choice, but you may find it to be a very valuable and helpful experience.
Other ideas. Take an English class, join an English group, find a tutor, read English magazines. Do whatever you can to immerse yourself in the language.
This means to pay attention to how you use English. Think (a little) about how you are going to say something before it comes out of your mouth. But don't think about all of the problems you have in English at the same time. Just choose something your know you are having difficulty with and work on using it correctly. For example, if you know that you have problems remembering to use a, an, and the, spend a few days trying to put them into sentences as you speak. Don't worry about anything else. Concentrate on that. When you feel that you are improving, choose something else to work on. Just keep trying and little by little, your English will get better everyday.