Much of what I learned about writing Statements of Purpose (SOP) comes from my four years working as JET Program Coordinator. In the days leading up to interviews, I'd be quickly reading through the applications and taking notes about interesting skills or experiences to talk about. Given that the SOPs were just about the only spot where a candidate could stand out and have an independent voice, it was pretty disappointing that most of them seemed repetitive and trite. After about the fourth or fifth one in a row, I would actually feel irritated towards applicants for trying to create a meaningful statement instead of just giving me the information I wanted and needed to know. I quickly came to hate phrases like "build a bridge," "it has always been my passion," "serve as an ambassador," "for as long as I can remember," "Japan has always been my dream," etc... All of these phrases are accurate reflections of what the applicant was feeling at the time of writing (and my own Statement of Purpose was probably identical to theirs), but it does not take the reader's needs into account. It also doesn't take into consideration how much these emotions and expressions directly mirror their peers'. As such, the impact of these statements is lessened because they're so common.
While I do want to assure all of the JET Program applicants I interviewed that I was always (or nearly always) over any element of frustration by the time I interviewed them and definitely always tried to be fair and even-handed towards everyone I saw, the experience was very informative of how a reviewer sees and processes applications. When you have tens to hundreds or even thousands of applications to go through, you will most often have a positive response to the ones who put aside the desire for a personally meaningful statement and instead craft it to exactly match what a reviewer is looking for. This is essential to making a savvy Statement of Purpose. It can still be meaningful (and, indeed, it should still be well-written, thoughtful, and personal), but the major goal is to demonstrate fit and suitability rather than expressing your deepest wishes and goals.
The Statement of Purpose spells out the qualities, experiences, traits, abilities, and unique elements that make you a good match for the opportunity you are applying for. It is not about expressing yourself, it is about providing your best-framed argument for why you are a good fit for this opportunity, why you want to do it, and what you can offer.
What I learned from over four years of reading JET Program Statements of Purpose helped me immensely as I wrote my PhD applications and then later my fellowship applications. In fact, after I went through my fellowship application process, I worked with two administrators for fellowship programs at my university to put together a workshop on how to approach applying for fellowships. In the process, I learned a lot from these administrators as well, and I incorporated some of the more important points into my guides.
My guide on writing SOPs goes into much more detail, but I wanted to spell out some of my personal approaches and suggestions here.
1. Do some role-playing. It's really useful to start off your SOP prep by viewing yourself from the perspective of a reviewer. Consider what you know of the opportunity (whether it be a graduate program, fellowship, or job) and ask what types of experience, aspirations, or personal qualities you'd be looking for in an applicant. Write down how you match each of those, and then start shaping your SOP around those answers. This should be a good confidence booster (and it's a good exercise before any interviews you may have to do, too). Don't forget to consider the scope, objective, or history of the opportunity as well as any particular parameters that are important to address for fit, suitability, or eligibility.
2. Answer the basic questions. There were some years where I started every interview with the question, "So, why do you want to do the JET Program?" I even started telling applicants in their interview notification email that they would be asked questions including things like "Why JET" or "Why Japan." Every year, I'd have less than a handful of people who had an answer ready for that question. It's not that they didn't intrinsically know why they wanted this job, it's that they had spent so long cramming for any "gotcha" questions that they didn't put together succinct answers for the most basic of questions. No matter the opportunity type, your SOP should be able to answer why this opportunity, why this location, why now, why you, why them, etc...
3. Answer the prompt. Most applications will have some sort of prompt or a series of questions that need to be integrated into the SOP. Your primary concern should be with answering these questions. Remember that reviewers are usually reading these very quickly (especially in the earliest stages), and they want to see the answers clearly and directly. You can be creative in where and how you address them in your statement, but make sure it's a succinct and direct answer.
4. Address your past, present, and future. A lot of SOPs focus on past experience and history to the complete or near complete exclusion of your current status and future aspirations. Especially with graduate schools and fellowships, you need to demonstrate current interests and skills as well as future educational and career goals. Even with jobs, especially one like the JET Program, you want to demonstrate that you see it fitting into a larger trajectory and that you are good Return on Investment (ROI) material.
5. Beef up your first paragraph. Your first paragraph is the most important section in terms of setting up expectations and giving your application a voice. When reviewers are examining your application for a second or third time, the first paragraph should remind them of what's interesting about you and what they'll find in the rest of the application. It should briefly address the opportunity you're applying for, why you're applying, some of your qualifications, how the opportunity fits into your future goals, and something unique and memorable about you. That element could be an unusual quality and qualification that perfectly demonstrates your suitability for the opportunity, or it could an unusual personal trait or experience that gives you a unique perspective. It could also be something that you're a little unsure of how to address elsewhere. For example, I wasn't sure how to shine up the fact that I had taken a four year break from academia in my SOP, so I decided to lead with it and make it a positive feature.
6. Aim for the "read again" pile. It doesn't matter what a fantastic piece of writing your SOP is upon deeper reflection, if it doesn't make an overwhelmed and exhausted reviewer put your application in the "read again" pile, then it hasn't served its purpose. While your ultimate goal is to be successful in your application process, the first cut that separates the suitable applications from the unsuitable ones is the biggest one you need to survive. That means you should prioritize clarity, directness, accessibility, and answering the questions or prompt.
7. Avoid jargon and showing off. Jargon is field-specific vocabulary, which can serve as an identifier of your awareness of the field as well as a demarcation for insiders or outsiders in your discipline. Jargon is very off-putting to a lot of people, and if used incorrectly it can sound pompous or ridiculous. It is important to sound knowledgeable of your area of expertise, but it's more important to be inclusive of all readers and be able to clearly explain the important points of your SOP. Not everyone involved in the selection process will be familiar with your discipline or even your exact frame of reference, and they won't appreciate being excluded. Focus on clarity and directness more than attempting to sound intelligent.
8. Don't self-eliminate. Graduate programs need graduate students, fellowships have to be given away, and jobs have to be filled. The people reviewing applications aren't necessarily looking for the individuals who will pass an invisible bar separating "good enough" from "not good enough," they're looking for the best matches for the opportunity. Don't let imposter syndrome or fears of inadequacy hold you back. The only way you are 100% guaranteed not to get the opportunity is to not apply for it.
9. Don't take rejection personally. Even if you are ultimately unsuccessful, it is rarely the case that you as an individual was rejected; quite often, the application package that you put together was not as good a match as the ones you were competing against. If this is an opportunity that you want to keep pursuing, then take some time to evaluate your skillset, approach, and qualifications to see if these can be polished up or improved. There are also cases where the rejection had nothing to do with you or your application; there may have been a cut in openings, a professor you wanted to work with isn't taking new students this year, a workplace needs someone with a different set of skills and experiences, a reviewer saw your application after reading a spectacular one that made yours unfairly pale in comparison, etc.... You can't control these external elements that let to your being rejected, and another attempt might end up with a more positive ending.
10. Develop your SOP instincts. Especially if you're planning to be in academia, you're going to be writing Statements of Purpose for the rest of your career. Work on developing a personalized instinct for what makes for a successful and unsuccessful SOP by reading a lot of different examples, including from other disciplines or careers. Do not just focus on the examples of "good" statements. I honestly learned more about how to write a savvy SOP from the various uninspiring examples than I did from the good ones. Also, just because someone was successful in their overall application doesn't mean that their SOP was especially good; it may not have been, but it still did the job to get the applicant to the next stage. By the same token, an unsuccessful application could have had an excellent SOP but lacked essential qualities, experiences, or documentation necessary to meet eligibility requirements.
I hope that's helpful! Be sure to look at the actual Statement of Purpose guide as well. Specific statements will vary depending upon the opportunity type, and I did try to address that in the guide. I nonetheless felt it was still worthwhile to address SOPs for graduate school, fellowships, and jobs together in the same document, as the advice and insights can overlap quite a bit. Keep in mind as well, I'm still learning myself. Any information listed on this website is merely a reflection of my experience and perspective and is liable to change as I evolve as a scholar and person.