There's no such thing as an unbiased source in history. A large part of a historian's training is learning how to identify a source's bias and how to use its data in your narrative while recognizing the author's bias. Whenever a historian reads a primary or secondary source, we immediately think:

• Who wrote this? I'd wager that almost every historian will Google the author of a book that they start reading to find out who they are as a person. Does the author have religious, ideological, class or nationalistic interests that might compromise the integrity of their narrative? Do they have the requisite background knowledge to make authoritative statements about a particular historica subject? It might not be a good idea to read a book about the USA's founding fathers that is written by a conservative news pundit who has no background in history, for example.

• Why did they write it? Every text is produced for a reason. Did the author write a book or article because they have studied a topic for years and wish to contribute to our collective historical knowledge, or do they have an ideological agenda that they wish to further? Is the author's thesis an attempt to challenge the dominant historiographical model of a particular period in time, or is it an attempt to argue for an ideological position using (or probably misusing) historical evidence as a crutch? A good way to differentiate the two is by asking yourself whether or not the author's argument is explicit or implicit. A good secondary source will have an explicit argument that is present throughout the text, while a bad and biased work will likely have an implicit argument.

• What is the text's intended audience? Did the author write their work for other academics, for the general public or for a certain demographic in the general public? Unfortunately, not all sources are equal and you should stick to the first kind that I've listed: works written for an academic audience. I'm not saying that works of popular history are all bad and you should feel bad for reading them (popular history is actually a good jumping-off point for many people interested in history, it just has very limited uses after that), but if you want to properly educate yourself in a historical subject you must get a feel for the historiography of that subject which requires delving into academic texts. My own personal rule of thumb for this is: would I be comfortable citing this text in a university-level history paper? Following this rule, if I wanted to learn about the Eastern Front in WWII I'd pick David Glantz's When Titans Clashed over Dan Carlin's Ostfront podcast series.

• What does the author omit? Sometimes the best way to tell if a text is biased is by reading for what the author doesn't write. That sounds kind of confusing, but imagine you were reading a book about the Eastern Front in which the author did not mention the Holocaust or German wartime atrocities, but did write about Soviet atrocities. That would be a pretty big indication that the author has a huge and gross bias.

This can all be applied to primary sources as well, but seeing that you're interested in starting to learn about history, you should stick to secondary sources for a while. It's a classic rookie mistake to take primary sources as completely unbiased because you don't understand the historical context in which they were produced: look at Holocaust deniers who literally use Nazi propaganda about how great concentration camps were as historical fact. They don't know, or don't care to know the context of those propaganda pieces and misuse historical data.

This is my guide for ancient history. I'm going to assume you've got a bit of time on your hands. If not then just skip 3b-7.

1. Read something about the period you are interested in. So go to Wikipedia and off you go. Wikipedia is actually pretty good for ancient history.

2. Then check the Wikipedia references. See if any are available online. Put these into Google scholar to see if they are cited often. This is not necessarily an indication of quality, but it might give you an idea if sources are well respected among scholars.

3. Find these sources. a) Some might require you to go to the library > go there.
   b) Some might only be available in French or German > Learn these languages. c) Some might require access online journal databases like JSTOR > If you are a university student, you're in luck, if not, try a library. Or maybe sign up for some classes to get access.

4. If you find some good ones, read these sources. Then look at the sources they are referencing.

5. By this time you should be looking at some primary sources. For ancient history, a lot of these will be available online. Those that don't should be available in decent-seized libraries. Read these as widely as you can. Go back to secondary sources for context when you need to. The more you read of primary sources, the better an understanding you will gain about secondary sources.

6. Compare with other sources. See where secondary sources match up. Think about how the secondary sources represent the material in the primary. Are there leaps of intuition, is there a bit of excessive filling in of a narrative with limited concrete information?

7. Repeat this process on other topics.

Regarding 'history is written by victors', I think perhaps it is better to say that history is written by a certain class of people. Educated, male, often upper-class writers. Ancient history, at least in the east where my focus is, is perhaps a bit of an exception. When writing is so esoteric, typically it is commissioned by kings or rich, powerful men. When studying history, it is always important to think about the reasons a writer (or someone who commissioned the writer) of a source might have for saying what they are saying. Who is the source targeted at? What is its purpose? What biases might be present?

My top tips to educating yourself about history:

1. Avoid "celebrity" so-called history books. Bill O'Reilly, Rush Limbaugh, etc. are very, very poor sources of history. Though they may get some facts right, their self-important and agenda-laden attitudes colors historical interpretation.

2. See if you have access to historical journals and articles through a college or library; databases like EBSCO, American History & Life, and Historical Abstracts are tough to search so I'd suggest getting a tutorial from a librarian on how to use them. Still, the articles they abstract and link to are typically fresh and offer newer, more nuanced perspectives. And the abstracts help you weed through subjects which may not be interesting to you.

3. Try to avoid books that ask rhetorical questions on the cover in order to sell books; "Who killed Lincoln" or "What went wrong in the Middle East" or "What caused our democracy to decline" are intended to be emotional appeals and it is sometimes harder to read between the lines and question the author's evidence, narrative, and conclusion. This can be a difficult one to really adhere to, but be careful of books that reaffirm your world-view; challenge yourself and question everyone. Chase down sources and see if what the author says really did happen the way they say it did.

4. Look at primary sources whenever possible.

http://www.timemaps.com/history

This is a really great resource if you're just getting started. It's a series of maps of the political situation in the world at different points in history, with a bit of information about specific regions at each time. When I was initially trying to get into history, I was overwhelmed by the sheer amount of information there was, and I had no idea where to start. This website is great for getting a general sense of how things progressed over time, so that you can understand things you go on to read in their broader context.

Also, I'd suggest that when you want to delve into a subject in detail, you go straight for the books (or journal articles). I spent a long time trying to do research online, and while you can get a cursory understanding that way, books are just so much better. Particularly for sub-Saharan Africa, for which there is practically no information available online. Also, personally, when trying to learn about a particular time period in a particular region, it always helped to start reading a bit before the period I was interested in, so that I had a bit more context for what I was reading. Don't know if that works for everyone, just my experience.

The other commenters here make good points, something I'd add: if you are a college student and you have off-campus access to university resourcs - JSTOR, T&F Online etc - then go nuts. It's a brilliant source of really interesting stuff.

Just to add to what has already been said, try to rely on academic source material as much as possible. It has already been mentioned to stay away from celebrity writers. Double check every author. I see a lot of journalist write history book. Though that does not make their books wrong, it would be inadvisable for historians to use their book for secondary source material. Their books are fun reads, but not serious history in relation to historical research.

Your are probably going to be looking for someone trained a historians and will more than likely have a PhD. Their books/journal articles will be published by an academic source, university presses are popular, but there are others. Also, who is reviewing the book? It will not be USA today or People. It will be other academics.

Why is this important. This research are published after a lengthy peer-review process. Basically, other academics and professionals in the field are sent a historian's article/book and go through it with a fine-tooth comb to make sure that its as accurate as possible. This take roughly a year. If anything adverse if found it is rejected. Lastly, consider that these historians do not get much money at all from this. It is more about reputation than money. Something you see listed in the New York Times is making money. Motivation can make a world of difference about quality and accuracy.

PS. If you are put off by the "victors" of history, consider looking at Social History. It is still a young discipline, emerging in the 60s and 70s in response to the Civil Rights movement and Feminism. It is referred to as "history from below" because it studies the poor, minorities, etc. The people who have usually been ignored in the past.

Read books published by a University press. That's really the best way to get a good source on a subject. Also verify that the author not only has a Ph.D, but also is or has actively taught at a university.