Before the above question is taken up (to this about the answer), try to answer the following questions. These answers would guide you in answering how to become a successful speaker of English.
1. How did you learn eating ?
2. How did you learn walking ?
3. How did you learn to speak mother tongue?
4. How did you learn (if you know) cooking?
5. How did you learn (if you know) swimming?
6. How did you learn crossing the road ?
7. How did you learn (if you know) driving ?
8. How did you learn playing a sport ?
9. How did you learn posting a letter ?
10. How did you learn any art / craft that you know?
The only answer and the simplest answer to all these questions is: "BY DOING IT " So you can learn spoken English by speaking English. there is no other shortcut mothod to it.
Taking help from all the topics, you have to practice, certain expressions and use them in your speech, That is the only way learn how to speak English. However, you have to follow certain rules if you want to be a successful speaker, Then only you can convey exactly what you want to, to the listener.
1. Try to use the exact words for your idea. If you don't get it instantly, refer to a Synonyms Dictionary and try to learn as many synonyms as possible for that particular expression.
2. Make it a habit to speak English
3. Don't use any other language while speaking in English.
4. Be careful about the formal and informal situations and use the appropriate language.
5. Last and most important rule is, speak confidently. Even if you make mistakes, it doesn't matter. You learn only by correcting your mistakes and overcoming your shyness. So speak with confidence.