The topic of "language learning" is very broad, which often leads to frustrating conflicts in methods, learning styles, and advice. Therefore, one of the most difficult aspects of learning a language is simply getting past the noise of disagreement and dissent with regard to how you should do it, and why everyone else is wrong.
All too often, I find people having arguments about such mundane topics as why you should or should not worry about grammar, whether input or output is more important, which language is more difficult, or worse — people arguing about why each other's advice is invalid because they used the wrong term to describe something.
It's unproductive, but a lot of it can be avoided if you just make sure you know what your language goals are, and you tailor your learning to fit those goals.
1. Avoid the linguists
I have nothing against linguists — they're very intelligent people — but their interest in languages is primarily academic, and as such it tends to be quite at odds with my own.
I learn languages because I want to talk to people. Sure, I like all that academic stuff, but if I don't know the history of a language, or the right term for agglutination or devoicing or whatever, it doesn't stop me from learning to communicate with people.
Linguists hang out in online forums, anxious to discuss the intricacies of languages without ever spending much time actually learning them. They will eat up your time with pedantic discussions about the right or wrong way to refer to a grammatical detail or some feature of a language... and time is something you can never get back. Block out the linguists as much as possible and spend that time learning the language. You can come back later and learn the academic details of it afterwards, if you still care to know them.
2. Watch out for the test takers
Another group that I avoid are the test takers — the people who go around telling people they're "C1 in this language and B2 in that language". These standardized tests have a purpose: they're meant to give employers a way of ensuring a minimum level of competency for a job that requires foreign-language skill. But too many people wear them around as some sort of merit badge.
The test takers spend a lot of time talking about how many languages they know, how many words they know, what level they're at, or "what language should I learn next?" With them, everything feels like a competition: who knows more languages, and who knows each language better.
If you're learning your language specifically for a career-related purpose, then yes... these people may be able to help you with a study plan or something. But language learning shouldn't be a competition, and if your specific goal is anything other than "pass the test", then you're probably best served by avoiding these folks.
3. Literature lovers
There are many reasons why a person might want to learn a language solely for the purpose of reading, without any realy interest in ever using it to communicate with another human being. Some of the more common examples might include those learning Hebrew, Greek, or Latin for biblical study, or Arabic for the Koran, or those who learn Russian, French, or German for the purose of reading popular foreign literature as written by the native author.
If reading is your purpose with a foreign language, then by all means seek these people out because they are certain to have insights and stories to share, which you will find interesting. They'll have study plans that fit your goals, and they'll be able to suggest reading material that is sure to be interesting.
But if your goal is communication, rather than literature study, there is a good chance that these people will also slow you down. They're the ones whose advice always includes more and more input. And more importantly, none of their advice is geared toward actually ever saying something on your own.
4. Native speakers
Native speakers aren't universally the best for everyone. Most natives do not want to sit and talk about the fascinating linguistic qualities of their mother tongue. They certainly don't have any interest in what level you tested at.
If they're fans of classic literature, or religious scholars, the literature lovers may be able to find some common things to talk about, but when asked about authors they love, most natives are going to name someone current who you've never heard of; or more disappointingly, name an author who doesn't even write in their native language.
But if your goal is to communicate, native speakers are the best people to find (when you can) because they mostly don't care where you learned, they don't care what method you used, and they don't care about your academic appreciation for exotic grammatical constructs. They're ready to talk if you are.