English is spoken in many different countries, which means the language has different accents. Even within a country accents, and sometimes words differ. A native English speaker in the United States sounds much different than one in South Africa. While an American might say elevator, and British person will say lift. Someone working on English pronunciation needs to determine which accent is best to learn. Perfecting an Australian accent, and then moving to Ireland will still result in difficulty pronouncing the native tongue.
Get as much exposure to people speaking English as possible. Watch television shows broadcast in English, listen to audiobooks, and listen to friends, family and colleagues. Hearing proper pronunciation will bring out the subtleties of the language.
Practice English as much as possible. Ask friends to speak English constantly and start many conversations in English. Only hearing the language will not help pronunciation; you must speak in English as well to improve. The speaker can also focus on particular difficulties, like using an "l" sound in place of an "r" sound, or learning the difference in pronunciation between "good" and "cool".
English is a difficult language to learn, without worrying about pronunciation. Similar combinations of letters result in different pronunciations, and vast differences in accents can make perfecting pronunciation frustrating and difficult. Despite these difficulties, it is important to keep trying. Many people will be willing to help you practice if you ask.