You can't.
Phonetically, unless you moved to an English-speaking country within the age of, say-5 you can't sound like a native because your phonology and perception adjusts to what you're used to hear. (That's why sometimes we have trouble distinguisting between sounds). Don't bother trying to sound like a native, because:
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There is not a single accent to refer to (Wanna learn RP? Nobody talks like that. Like Beckam? Only in the south and London). Retain yours and get sensitized to accent differences, that's my advice.
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Nobody wants to hear you trying to sound like them. A single misplaced sound makes you fall "out" of the boundaries of an RP speaker or Estuary English speaker. Again, just don't bother, really.
As for other issues concerning language: grammar, vocabulary, syntax. Use grammars but damn, be ready to accept those rules being violated by speakers all the time. Language is shaped by speakers, not by books. Always remember that. So listen to PEOPLE, not CDs.
That's the best advice I can give you. Best wishes.