As others have mentioned, the process of writing an essay is totally based on what works for you personally. It all depends on how you like to organize information and what your strengths in writing are. Sometimes, though, the hardest part is knowing where to begin!
For me, the best way to start is by reading the question or prompt carefully, and if there's no prompt, then I start by thinking deeply about the topic and the stance that I want to take in my paper. Then, I jot down a few key points that I want to make sure to make in my essay. This way, I can be sure that the essay is focusing on what it's supposed to and that I have a good direction to start in as I make my outline.
Next, I make an outline. For me, this step is crucial, but not for everyone! I find that an outline helps me organize my thoughts and prevents me from rambling on in my paper. Also, an outline can help organize the structure of the paper to make it the most effective it can be. For example, having a basic map of the points I'm going to make in my paper helps me decide where to insert counterarguments or pieces of evidence where I think they would be the most beneficial. Here's what my outlines look like:
(I like to write the introduction last, so I don't focus too much on this part.)
Body Paragraph 1-
(Repeat for as many body paragraphs as you need to make all of your points)
Counterargument (if necessary)-
Point to be argued against
Evidence to support
Restatement of thesis
As you can see, my outline isn't all-inclusive, and there's still a lot of writing to do. However, it gives me an idea of where to start and where my paper will be going.
Finally, I write my thesis statement and fill it, along with a restatement of it, into my outline. A thesis statement is basically the sentence that summarizes the essay's main point, so it might be helpful to do this before you make your outline if it would make it easier to fill in all of the main points of your body paragraphs that way. For me, writing the thesis statement is kind of an annoying step that I like to save until after I've gotten all of my thoughts down because my main challenge in writing it is that it's hard to fit all of my ideas into one sentence.
From there, all that's left to do is turn the outline into an essay! Of course, this is the main writing, which will take time, revision, and editing, but I find it's a lot more manageable once I have organized my main points, evidence, and structure of the essay.
I hope this helps! :)