The International Phonetic Alphabet (IPA) can help English language learners perfect their pronunciation by giving them a method for learning and practicing English sounds. The IPA provides symbols that correspond to each of the sounds in the English language. Have a native English speaker write a sample word that corresponds to the sound that each symbol represents. Then, find an English dictionary that features IPA phonetic spelling. Practice each of the word's sounds individually; then try to put them together to pronounce the entire word correctly. You can also practice using the numerous IPA pronunciation exercises available online.
Different sounds are made by moving your mouth and tongue in different ways, restricting or allowing the flow of air and changing the shape of your lips. Learn how the English sounds you are struggling with are made; then try to improve your pronunciation by making a conscious effort to physically produce them.Spend extra time learning to use your vocal apparatus to produce the most common sounds in the English language, like the "schwa" sound.
If you constantly have trouble with a few tricky words, find a word or a phrase that helps you remember how those particular words are pronounced. For instance, if you're having trouble pronouncing the word "tired," you might remember it by thinking that it sounds like a car tire with a "d" tacked to the end of it.
The more you hear spoken English, the better English pronunciation you will have. When you hear English words said over and over again, pronouncing them correctly will eventually become second nature. For this reason, it's important that you surround yourself with English as much as possible, whether this means watching English television or going to an English-speaking country.