Many a question can be answered here on /r/askhistorians, but sometimes a question goes unanswered or even a request for sources unheeded. Someone new to an area however wouldn't know who else to ask, or where to begin, leaving them vulnerable to finding texts which seem to be comprehensive, but in practice contains numerous errors.
Far better that we each find somewhere to begin ourselves, and consult when we've questions that are less nebulous than "What was this thing?".
The obvious answer is books, but the trick is figuring out WHICH books to read. Finding a book on a topic is usually simple enough, especially with e-books.
Once you have a book a good first step is to look at the author and find out who they are. Jump on Google and look up the author, what is their field, are they actually a historian or just some random person? If they aren't a professional historian does their background give them some unique inside into the topic of the book? As an example, say you have found a book on espionage and the author is a retired CIA agent, they may not be a professional historian but their experience gives them insite into the subject matter.
Second step is to look at the publisher. Many publishers specialize in publishing academic history books, but this isn't a deal breaker per say. A lot of Universities will publish their own books, but If the author is a credible historian with a long resume and THIS particular book happens to be published by a less academic publisher, that isn't necessarily a deal breaker. What should be a deal breaker is if the author is not a professional historian AND the book is not published by a reputable publisher.
This is actually one of the most difficult questions in any field. Part of the benefit of higher education is that the information is usually vetted, and curated or presented to you in a way that will introduce you to the topic.
In the case of history, you can often start with a book, if you know the right author. Often times famous novels can be a good place to start. However they can be problematic. If you were asking about the formation of the modern middle east, or post WWI negotiations, I would start you with David Fromkin's A Peace to End All Peace.
You might be surprised, but you can do a lot worse than wikipedia, or even certain youtube infotainment channels. The real value is for you to find a beginning source that will give you an overview of the period and the entities involved. Learning about the Teutonic State might lead you down a rabbit hole about the Baltic Crusades. Learning about the Bosnian War might lead you into reading about the Column of Tuzla that fought through Serb controlled countryside from Srebrenica to Tuzla over the course of a week. For ages the UN had access to their reports directly online. They still might, I just don't study in that field anymore.
In general, academic sources, or vetting a good author as others have mentioned, or his publisher. You could also look at what kinds of awards their books may have won. Jared Diamond and David Fromkin are award winning authors whose books are at least taken seriously amongst academia. Niall Ferguson, for example, is not.
I would seriously encourage you to call your local college library and apply for membership. Not only will they carry the top 10 or 20 books per any given subject, they'll also have access to inter-library loan and online academically vetted source portals like JSTOR. If you're looking for the Theodore Ayrault Dodge book on Gustavus Adolphus, for example, you can get it through there without having to spend $60 on amazon or whatever it's listing for these days.
Hi Cataphractoi,
You may be interested in the following /r/AskHistorians resources:
I don't know how feasible it is or how much you would want to but doing even a little bit of history in a university will definitely help. If you're not aiming to do professional history of a post-grad degree you can just do some undergrad units, those classes can help start. It also provides you with a university account that should make doing your own extracurricular research significantly easier with probably access to places like JSTOR and EBSCOHOST.
Without a university subscription, and also with it, I would also ecommend Project Gutenberg. They're particularly good for hard-to-find primary texts (obviously there are less good for up-to-date journal articles since they are mainly older public domain things, which is where a university subscription to JSTOR is super helpful).