Can someone explain to me how what the historical method is and how to practice it?

The historical method, as I understand the application of the term in the English language, usually refers to source criticism and hermeneutics, meaning the identification and evaluation of sources and their subsequent interpretation.

While the principles of the historical method are still important to the everyday work of a historian especially in terms of source criticism, it only is part of an array of methodologies historians today use to write history with a plethora of additional methods and theories employed in order to formulate answers to historical questions in a meaningful narrative for the interested audience to consume. Hence, I will give an overview of how historians generally work and within that process demonstrate how the historical method is employed.

All historical inquiry starts with a question, something you want to find out. This can range from the huge question, such as what were the effects of modernity on society or what factors lead to the start of WWI, to the very small, such as how did the Civil War affect rural miners in this one Appalachian town. Historians usually formulate these question under the impression of several things not just out of thin air:

First, there is the mode of historical thinking. The American Historical Association has a very worthwhile text on the subject here that describes the way historians think. It formulates this way as the "five C's": change over time, causality, context, complexity, and contingency. The text goes into depth on these concepts but it is important to stress – as the author does – that this is something that develops with practice over time and does not necessarily represent a checklist.

Second, questions posed by historians in their research are usually formulated under the strong impression of knowledge of the subject we are asking about. That is why we usually specialize in an era or subject. One is usually never the first one to write about a subject and finding a new and interesting question or finding a new and interesting answer/approach to a question that has already been posed (e.g. what factors lead to the start of WWI?) is an exercise in historical thinking and skill. After all, taking into account both complexity and contingency in history, finding the definite answer to a question is impossible and writing the same book as somebody else makes little sense.

With the same foreknowledge of the subject that we use to formulate our question, we also usually form hypotheses about the answer and chose our approach on how to tackle our question. Influenced by what question you ask, the methodological and theoretical approach can vary. A question on the Appalachian miners is best suited to an approach such as microhistory, where we focus on sources from a very small space that is taken to be somewhat indicative for what we want to explore while a question on the origin of WWI can profit from different approaches such as cultural history or approaches influenced by theories of international relations.

Having determined our question and our broad methodological approach, we can turn to looking for and interpreting sources. And here is where the historical method is usually employed. By asking several questions about a specific source, we evaluate its worth for undertaking, its reliability and place it into the broader context of other sources and knowledge we have of certain events and developments. At its basis, the historical method makes us ask the famed "w-questions": When, where, who, why, what and how. Meaning, when was a source produced, where was it produced, who produced it, for what reasons/purpose was it produced, what does it say, and how does it fit into the context.

For assessing sources we take both their inner and outer forms into context. Let's say you have a written document: The formal set-up of said document (such as a "top secret stamp" or the way it is internally structured) can immediately tell you something about its origin or reliability: A diary looks different than a government document and the former is a different genre as the intimate thoughts of one person are to be read and interpreted differently than the official account of a government official.

Also, in terms of what does it say and how it fits into the context, the answers to these questions are always formulated again with our question and chosen approach in mind and also go into the territory of evaluating how useful a document is to us in the first place: The description of the start of WWI from the perspective of a diary of a citizen of Berlin can be an invaluable document when writing about a cultural history of WWI or a microhistory; it is less useful in determining what factors lead to the outbreak of WWI on an international level.

From a variety of sources taken together, historians then will try to formulate and structure a meaningful narrative that interprets these sources together in an attempt to answer the question we set out with. This is done by contextualizing these documents both in terms of knowledge of the subject area as well as with each other. A citizen of Berlin is going to have a different perception of the start of WWI than a rural farmer in Bavaria and correlating these things together to form a useful narrative and interpretation towards an answer to our initial question is the real chunk of work. This again is somewhat influenced by our wider approach since what kind of history we write is going to influence how all that fits together.

This all sounds rather formulaic and in the reality the process we employ to do all this is a bit more messy and also goes on at the same time rather than in a step-by-step process (what kind of sources we find can change our approach or influence our question and hypothesis and so forth) but the main point is that the classical historical method, as in how we evaluate, read, and interpret sources is only part of larger process that is employed in order to arrive from a question posed with previous knowledge of the subject in mind at an answer in form of a meaningful interpretative narrative.