Absorb a lot of English. Read English books, websites, and magazines. At first, you will probably need a dictionary, but if you practice often, you will be able to understand words in their context. Only read what you would enjoy in your first language: if you don't, you will get bored very easily. Watch English-language television and movies. This will help you to learn normal conversational English. It is also very good for your accent. If you find it too tough, try and watch movies with English subtitles: even if you don't understand every word, you will probably get the meaning of the story thanks to the images. It might be slow at first, but both reading and watching movies in English are really useful if you practice often.