When it comes to American English, you must really know what it means to speak fluently. There are some rules to be perfect in speaking American English. This type of English is possible only with right accent. If you have right accent, then you can speak american English nicely. I am giving here some 10 to 15 important tips on how to speak it with out problem.
The one way is to completely spend your time watching English movies daily for a period of six months. Without this practise of listening I doubt you will speak American English perfectly. So try to watch one English movie every day where we have lot of conversational English rather that business English. This will really help you build up strongly your areas of interest. Do not just taken up by books. Reading may not really help you to learn it.
Smoothness is the secret of such English. Try to speak as smooth as ice cream. Do not harden your words while you speak. It must be like a flowing water. There must not be any stammering or such ugly accent. American English is highly smoother. So practise this every day by doing loud reading.
Staircase intonation also will help you. This means that when you speak you must come down gradually. Americans do this way when they speak any sentence. This is called coming down from staircase. This type of intonation will help you to really learn american accent.
Stress also plays an important area when you speak English. Try to know how to use stress on syllables easily. Stress makes you perfect. This is quite difficult unless you know exactly where must be the stress in a word.
Try to also make sure you are confident enough to change you accent. Avoid local influences of your own language with that of American English. This way you will be successful in speaking good English as the days go by.