If you live in an English-speaking country, you are forced to use English every day. If moving to an English-speaking country is not feasible, attend a short-term intensive English course in an English-speaking country. Or just spend some time in an English-speaking country, preferably staying with an English-speaking host family. With even as little time as a week, you'll notice improvement in your language skills.
Use English every day. Read newspapers, magazines and books. Listen to news. Write a diary in English and a letter to a friend. Speak with your English-speaking friends. The Internet is a great way to improve English--you can read, write, listen and chat. Taking a one-week intensive course in your home country is also a good idea. Try to go where English-speaking people gather, such as English or Irish pubs, and restaurants that are popular with English-speaking tourists and residents.
If you are into gardening, for instance, try to master all gardening words in English. Make English-speaking friends through gardening clubs or groups. Learning English is much more fun when you combine your hobby or interest.
Try to think in English as much as you can. Spare one hour everyday for thinking in English or saying what you are doing in English. If you are cooking, think or say, "I am chopping broccoli." If you have a pet, speak to it in English. If you need to check some words, use an English dictionary, not a translation dictionary. When you think in English, do not translate into your native language.
Teach English to your friends, small children or elderly people. Volunteer at your local American school, English-speaking events and activities. If there are no groups you can join, set up your own English-speaking club.
Set a realistic daily, weekly or monthly goal. Write an English blog daily. Read a book, and write a book review once a month. Enter writing, speech or reading contests. A great way to check your level and force yourself to study is to take English tests, such as TOEFL, TOEIC, IELTS or local English proficiency tests. Get English teaching certificates or degrees.