Move to a country that speaks that language and pretend you don't understand english when they try

don't look for a best way, just get busy studying. The worst learning methods still beat endless searching for the best.

If you must look for a best way, at least look in your target language.

Get a girlfriend who only speaks that language.

I think Krashen's "Natural Approach" is the best way to learn. It focuses on consuming comprehensible input (CI) - listening/reading in the foreign language, and making sure you understand around 80%+. The idea would be to start with very easy stories/sentences, and slowly build that up as your vocabulary grows.

Pimsleur & FSI are good resources. Also, try to watch movies/shows that you already have seen in the target language instead (e.g. Friends, The Office, Simpsons). That way, you already have the context, and it will be easier to comprehend.

You need around 100-200hrs of CI to have a basic understanding of the language (maybe you can't speak, but you can understand basic interactions in the language). At around 400-600hrs, you'll be intermediate, and after around 800-1000hrs of CI, you'll be fluent.

I honestly don’t know. I’ve always been extremely good with languages. When I was 12 I learned enough German to chat with people, by hanging out in German chat rooms on AOL.

So I’m lucky, and I can only advise the other lucky ones.

If you’re like me, I recommend starting with a book titled “Learn X” or “X in 30 days”, that sort of thing.

And, do that while you’re traveling in that country. Every single thing you learn, go out and use it. Have google translate or something on hand to fill in where you can’t do it.

Also, get good at connecting with people nonverbally. That gets you the goodwill that you need to access practice when you suck at the language. Get good at eye contact, at observing how people are behaving and fitting in. Be respectful. There are universal human signs of respect and they fill in decently well when you don’t know what to do. For example, the down-nod is a human universal (in fact I think it’s an animal universal — I’ve noticed even birds and dogs seem to chill about my presence when I give them a little bow or down-nod).

Then, as my father who has done intense language training for the army recommends, find a way to be both speaking and listening.

After you start getting the grammar, memorize shit tons of vocab. Get an app with like 10000 words in your target language and just work on it every day. Brainscape is cool; they’ve got a nice system for tracking confidence and presenting what most needs practice.

Watching TV is great for training the ear. Here is the key thing though. So many people find this so hard to do. It’s easy, but people resist it so hard:

Let go of understanding what they’re saying. Listen to them speaking, like you would listen to music or nature sounds. Don’t rewind it. Definitely don’t turn on the subtitles, even if they’re in the foreign language.

Also listen to podcasts. It’s useful to train different modes:

• Watching and listening
• Watching their mouth and listening
• Watching the show’s overall action and listening
• Listening only
• Listening only with your left ear
• Listening only with your right ear
• Listening at low volume
• Listening while in a noisy environment

etc. All those networks overlap in your brain, but not completely. As the old man in Blues Guitar Inside and Out says to the kid

Getting sharper at anything makes you sharper at everything

To that end, it’s okay to train extremely deep. Like, if you spent 30 minutes just repeating one phrase and trying to perfectly match the intonation, pronunciation, rhythm, and tone of a native saying a phrase or sentence, that is not wasted time.

One from Bruce Lee:

I do not fear the man who has practiced 10,000 kicks once. I fear the man who has practices on kick 10,000 times.

If you can learn to say “rouge” (French for red) in exactly the way you hear a native speaker saying it, it will make all your French better. It will help with listening. It will help you understand things I can’t even put into words here, but are worth understanding.

I don’t know if this is useful for your average joe but if you’re like me and pick up languages easier than most, these techniques will probably help.

The most important and, for some reason, the most ignored advice I can give is that letting go of understanding. Whether it’s TV or real life, watch the person’s face. Absorb their emotional state and everything you can, and even imagine the feeling of communication. Actually listen, intently. But don’t worry about the things you don’t understand. Don’t worry if you understand nothing. Listening to people speak language we know nothing about is how humans learn language, and if you approach it just right you can activate that baby brain that just knows how to absorb it.

Listen the way your dog listens to you when you talk to him. Perk your ears up, make eye contact, tilt your head, and empathize. Once your brain realizes that you value what the person is saying, it will switch modes and you’ll fly through the acquisition.

Immersion.

Are you young? Move there, get whatever work you can. You'll speak the language enough to get by within 3-4 months (depending on how much the language differs from your own). By 2 years, if you have an ear for accents and a little ability to mimic, you can be fluent enough to pass for native. It really helps to take language courses at the same time, or else you'll find your conversational skills to be excellent, but your reading and writing skills will suck.

https://noun.town/games/

Used in VR, it offers some great immersion learning without any pressure.

Total immersion. Nothing else comes anywhere close.

Practice every day. You’ll find the best way for you by working at it at least a little each day and not giving up.

If you're trying to learn a somewhat common second language where you live, and you want to supplement / reinforce other learning, I'd suggest changing how you watch television. Instead of watching, say, Stargate (bc someone mentioned it below) in English, watch it with the German soundtrack and English subtitles. You'll still be entertained, but you'll be learning as well.

You can also do something similar, usually with more language options, if you borrow movie DVDs from your library.

Do you know how, near the beginning of the Stargate movie, the leader of the Egyptian-like peoples was given a chocolate bar so they could extract the word for "good", and then the linguists from both cultures went around touching random objects naming each one? That's a good representation of how language learning would work if you were choosing something effective. Apps mainly don't 100% go that route and aren't taking the best modus operandi.

Use it.

Immerese yourself into the language. Do everything in your power to convert your surroundings in such a way, that you're forced to use the language:

• change your phone's language
• join chatrooms, websites, gameservers, etc.
• do tandem
• watch shows/movies in that language
• read books, magazines, etc.
• practice grammar and extend your vocabulary

If you are trying to watch movies or series to understand a language i have a tip : don't select the best movie or series from the language you'll get too immersed and watch it in english dub to understand and enjoy it better (thats what i did).

Things like this help:

https://www.newsinslowspanish.com/

I am learning german. The way I am learning is actual language lessons and then a language learning app like duolingo to help with remembering vocab

Perhaps find somewhere local that offers part time courses, maybe a college etc. Or volunteer somewhere in an Italian community, for example, if you want to learn Italian.

I have no idea if the second idea would work but if you surround yourself with people from different cultures, maybe you might pick up words and basics.

Just a thought. Good luck!

Please define "best".

Fastest?
To what level of competence?
Thorough / complete?
Accommodating the languages you already speak?
Grammar heavy? Vocabulary heavy? Balanced between grammar and vocabulary?

It might help to explain what your use of the language will be. Tourist? Academic? Moving there?

Some people are disciplined and can follow a self-made study course. Ie Duolingo, books, flash cards, etc.

Most people don't have the discipline or the interest, realistically. Learning a different language is a difficult thing.

In my opinion, the best way to learn a language is be forced to use it. So for example if you move to Germany, you're going to be forced to learn German so you're subconsciously and consciously paying much more attention.

You don't have to move anywhere necessarily though. For example I know Americans that speak fluent Portuguese. Why? They married a Brazilian.

I learned Spanish working with Cubans that didn't speak English. I already knew Portuguese so it was a lot easier for me, but I couldn't speak Spanish for most of my life. It was only when I had incentive to learn, did I learn.

Contact. Start with duolingo then move onto youtube start with small videos in the language and your native language usually by teachers.

Set a goal like one Duolingo lesson per day and or one 5 min video in the language with subtitles on in the target language when you're good enough.

Read articles on news sites in the language and pick a few words you dont know and look them up.

You could also use anki to make flash cards.

Look for local language meetups so you can practice.

Last and most important dont be afraid of making a mistake or not getting it perfect, its all about the process. Have fun

Immersion, Girlfriends, Apps, Textbooks, Lectures are all good methods but the underlying problem is consistency. To learn a language you need to spend hundreds of hours studying so it won't happen in a day or a week. The best method is the one that you like and you are consistent in it.

Born in a place where people talks it and learn from people older than you.