One of the fastest ways to learn English pronunciation is through www.howjsay.com. Most common English words can be typed in and will be pronounced out loud by a speaker on the site. Another site, www.howtopronounce.com, lets the user hear word pronunciations in more than 35 languages.
English words are exceptionally hard to learn to pronounce, as the language is unpredictable and does not adhere to any strict set of rules. For a more comprehensive overview, it helps to learn and memorize the English sounds of letters, singularly and with other letter patterns. It is also advisable to learn the International Phonetic Alphabet symbols, which will help you understand written pronunciation cues and note them yourself.
Also helpful is "American Accent Training" by Ann Cook. She includes a section, which tells speakers of different languages what specific challenges they can expect.
Of course, English is spoken as a an official language in more than 65 countries and pronunciations vary widely. Pronunciation differences between America and England are explained in this instructional video found on YouTube.
Even within the United Kingdom, English is spoken with distinct accents in Scotland, Ireland and Wales as well areas like Liverpool. Within the United States, a speaker can be pegged as from the South, the North or the Midwest. The film "Fargo" famously celebrated a Minnesota accent, while "Valley Girls" did the same for Southern California.