Before starting to learn any language, there's something you can learn that will make acquiring excellent pronunciation much easier for any language.
I'll illustrate with an example. Imagine you've just started to learn Swedish, and you've encountered the word "sjuksköterska". How on earth is this actually pronounced? I could tell you that it sounds something like "hwookhertershka", but that isn't much help at all.
Alternatively, I could tell you that it's pronounced /ɧʉːkɧøːtɛʂka/, or even [ˈxʷʉ̟ʷːkˌxʷœːtɛʂkʲa], depending on how specific I was willing to get. If you had the right set of background knowledge, these transcriptions would tell you all you needed to know about the pronunciation of this word, and you could pronounce it with a native-like accent immediately.
The system I used to transcribe the pronunciation of this word is called the IPA, short for the "International Phonetic Alphabet", and before I go on, check out this interactive IPA chart. Just click on the different symbols to get an idea of all the different sounds the IPA can transcribe.
This is a set of symbols that can describe the sounds of any language without a bias towards a particular language; the idea is that these can describe English phonology just as well as Swedish or even Mongolian phonology. The symbols are reminiscent of their common pronunciations in European languages purely for convenience's sake.
Now, you might think to yourself, "Why don't we just use the English letters to transcribe things, wouldn't that be simpler?"
Here's why this wouldn't work: Take the English words "win", "white", and "wide". The letter "i" in each of these words has a different sound (for most northern American English accents). So, the letter "i" would be ambiguous in our hypothetical transcription system.
Now tell me what English letter corresponds to the Arabic consonant "ق". It's "q" in the IPA, a sound that doesn't even exist in English.
How can we accurately transcribe each of these sounds with no ambiguity? The answer is to pick one sound for each symbol. In the IPA, the /i/ symbol represents the vowel sound in the word "tea" because that's how the "i" letter is pronounced in pretty much every other language that uses the Latin alphabet, and the /q/ symbol is the Arabic sound above. In the same ways, each of the other IPA symbols represent one sound that's been agreed upon. The exact sound pronounced can vary slightly in individual language transcriptions, but the idea here is consistency within the transcriptions of a single language.
Thanks to this system, you can glance over the transcriptions for a language you have no idea how to pronounce, and understand exactly which sounds a particular word is made of. You can even immediately pronounce this word with a pretty good accent! This is especially useful for languages with confusing orthography (like English or French) or for languages that use a writing system you might be unfamiliar with (such as Arabic or Hindi).
Once you've learned the particular nuances to each IPA symbol for a particular language, you can quickly gain a perfectly understandable accent without having to rely on years of passive input to slowly improve your accent. Good descriptions of language phonology and the particular sounds to each relevant IPA symbol can be found on a language's Wikipedia page in the format "language Language", "IPA for language", and "language Phonology".
With the help of just a few recordings from native speakers (on places such as Forvo to fine-tune how you pronounce each sound in the specific language, your pronunciation will be incredibly good, with way less effort than you'd put in trying to guess how each word you encounter is pronounced.
Hopefully I've convinced you to learn the IPA, and to glance over at a language's phonology pages at Wikipedia.
Good luck learning the IPA, and check out this post for more phonological goodies!