I'm a law student interested in legal history as an academic field of investigation and, since I don't have formal formation in history, I would be glad if you could give some advices (if you can append bibliography or else I would be very thankful with you)
The biggest issue I've seen (other than picking bad sources, which /u/AlviseFalier already went into) is a lack of understanding how the historical record can be distorted.
People are generally aware of "bias" and the idea that someone might recount events in a way that makes their "side" look better, but already, that's not the greatest way to look at history. (The "history is written by the victors" myth is from the same source. Lots of Germans wrote books after World War II and controlled the narrative for a time, i.e. the "clean Wehrmacht" myth.) Not only do you have to consider contextual factors like "was this account going to be called out as false if there is lying going on" but a great deal of historical distortion happens for more innocent reasons.
The same account, told over and over, has details get dropped or changed. Maybe one author used a flourish to make an account look more exciting, and further authors took that as fact. Maybe someone just made a typo. Maybe there was something mistranslated.
One of my all-time favorite historical papers is not by a self-identified historian at all, but a mathematician, writing about a story regarding the mathematician Gauss.
The author (Brian Hayes) regards a story which he remembered from other re-tellings, and he rendered as
In the 1780s a provincial German schoolmaster gave his class the tedious assignment of summing the first 100 integers. The teacher's aim was to keep the kids quiet for half an hour, but one young pupil almost immediately produced an answer: 1 + 2 + 3 + ... + 98 + 99 + 100 = 5,050. The smart aleck was Carl Friedrich Gauss, who would go on to join the short list of candidates for greatest mathematician ever.
He then wonders about what actually happened, and gathers an entire collection of retellings of the anecdote in the table here. Things get dropped, added, changed. The original version of the story mentions the teacher's whip, which gradually gets removed in later versions. He goes to the original version of the anecdote (the author Wolfgang Sartorius) and finds even when going that far back, the translation in English made slight (but important) change to the story. Here is (most of) the original, with the translation corrections in brackets:
Here occurred an incident which he often related in old age with amusement and relish. In this class the pupil who first finished his example in arithmetic was to place his slate in the middle of a large table. On top of this the second placed his slate and so on. The young Gauss had just entered the class when Büttner gave out for a problem [the summing of an arithmetic series]. The problem was barely stated before Gauss threw his slate on the table with the words (in the low Braunschweig dialect): "There it lies." While the other pupils continued [counting, multiplying and adding], Büttner, with conscious dignity, walked back and forth, occasionally throwing an ironical, pitying glance toward this the youngest of the pupils. The boy sat quietly with his task ended, as fully aware as he always was on finishing a task that the problem had been correctly solved and that there could be no other result.
At the end of the hour the slates were turned bottom up. That of the young Gauss with one solitary figure lay on top. When Büttner read out the answer, to the surprise of all present that of young Gauss was found to be correct, whereas many of the others were wrong.
Not only is the sequence not necessarily 1 to 100, but Gauss wasn't the only one correct, and the "counting, multiplying and adding" gives the impression that the other students weren't taking the exercise in a fully mechanical light. Hayes goes on to experiment with how one of the "other students" might approach the problem and realized that fairly quickly patterns come out which multiplying would help take advantage of.
The original problem was given in perhaps given in a sincere sense, but in retellings, the battle of student vs. teacher became embellished ("the teacher's aim was to keep the kids quiet").
And of course, this still isn't the end of the road -- after all this isn't even told directly by Gauss. This is Sartorius, retelling a story told by Gauss at old age, of Gauss himself at a young age. It is certainly possible changes and embellishments happened even at the earliest stage. The best historical approach will try to find corroborating events for everything possible, and know when to hedge -- that is, be aware of when something is true only in a probabilistic sense.
I think the most important thing to keep in mind is the quality of your sources: a good secondary source will cite the primary source they are drawing from, and it is important to understand when to engage with sources critically. I find that many non-historians researching history for personal projects often rely on the most readily available sources, including websites or pop histories which while fun to read, typically rely on "common knowledge" drawn from apocryphal conjecture, often traceable back to assumptions made by nineteenth century historians working without modern methodologies. Seriously, you have no idea how much modern "Common Knowledge" was pretty much made up in the 19th century.
Since you're a lawyer, I can try to offer a legal analogy: if the ultimate source for a historical assertion is a conjecture by a nineteenth-century writer, it's be a bit like basing a legal argument on a precedent set by pre-constitutional legal case. Sure it might be forgivable as a comment in a casual conversation, and we can't deny it might be part of the same tradition of thought which has been transmitted to the modern day, but if we want our work to hold up to the modern world we need to work within the confines of modern systems and methodologies.
What does this mean? For a lawyer, your arguments must be based on current interpretation of laws in force, from the constitution down to the details of the legal code. For a historian, this means basing arguments on something which will hold up to the scrutiny of modern peer review: will other historians be able to punch holes in this argument? Can I back this up with credible sources? Does this consider the latest work done by other people? And if we want to get very serious, have these conclusions been reached using modern methodologies?
Of course, there is a spectrum of common sense to be applied. A friend recently tapped me to help research an element of their family history, and I was able to dig up information from the website of local nonprofit. I did not scour the nonprofit's website for academic citations, but once I could be reasonably confident of their source material (documents in their archive) I told my friend this was reliable information. But if I had been researching an academic paper, I might have instead insisted on reviewing the source documents in order to cite them directly.
I am an amateur by all means, but let me share something I have learned and try and stick to.
People who study subjects they love and are passionate about, will naturally gravitate towards their chosen narrative, and often cite sources that support that while ignoring or explaining away those that don't. This can get particularly difficult when people get cemented down for whatever reasons- although it is expected and natural.
I always try to begin everything with "I don't know for sure, but-" and then cite why I think that (obviously when the topic is up for interpretation, not factual information). I use probably and most likely a lot because there's many things that to state as "this is fact" would be academically dishonest. What's important then is supporting that supposition with concrete evidence. That evidence may also be used to counter you, and thats fine, but there has to be an establishment of reality first.
2)Not all sources are created equal. Not all equal sources are created equal.
It's easy to find a book or paper or whatever that tells you what reinforces your inner, perhaps subconscience, bias. You have to look at so many things when considering whether it's worthy or not. When was it written? Who wrote it? Are they respected? Have they been sourced and quoted? Are the statements you disagree with at least supported by sources so that it's a legitimate probability? Under what context was this information presented?
If you have two equally respected, but contrasting, sources- you're going to need to look at where they are getting their info from. Why does this expert believe this and this one believe this? This is a rabbit hole and can take forever, but once you see where everyones working from you can begin to reconcile them. Even the best are wrong sometimes, or refer to the version they want or like.
For primary sources, you almost have to dive into the realm of conjecture, which is fine- but try and have a reason based in fact why you interpret something the way you do. It's OK to speculate. It's also OK if current interpretation isn't supported by first hand accounts- and it's ok to call that out. Primary sources are wonderful but can be tricky as they are created by fallible, emotional, humans.
I've been researching for decades, and I am wrong all the time. It's natural- something worms its way into my brain and mutates so when I need it, it's become something else. I'll missource photographs, make bad calls, be completely uninformed on something- and that's great! I often ask why I think that, which more often that not I can nail down to a source I trusted but should be reviewed. Also, it's not possible to know everything. You can be an expert in one thing and know nothing about a certain area of it. Learn, ask questions, be up front when you don't know something. It doesn't make you dumber or less knowledgeable- it makes you a better historian.
Ultimately, it's about being open to change and willing to go with it but also being ok with being reassured in an original opinion. It's about wanting to know the truth more than it is about wanting to be right.
At least for me who is, and I stress, an amateur with a hobby :)
