Recommenders asked too late. Asking a professor in November for a December deadline is how you get a two-paragraph letter that says you attended class. Ask in September. Hand them your resume, your draft SOP, and a short list of things you would love mentioned. Make it easy and they will make it good.
Ignoring the small requirements. Word counts. File formats. "Upload, do not mail." Every cycle, strong candidates get flagged for admin reasons that have nothing to do with merit. This is what an application completeness checker is for. It walks your file against the program's actual requirements and flags the gaps your eyes skipped.
Applying to too few schools, or too many. Four reaches and no safeties is gambling. Fifteen applications is burnout, and it shows in the essays. Most counselors land around eight to ten, mixed across tiers. I have no better number than that.
No second human on the proofreading. You cannot catch your own typos. Your brain reads what you meant to write. Get someone else to read it.
And a bonus, because five was not enough: not checking the portal after submitting. Portals flag missing items silently. Log in weekly until every item shows received. The application is not done when you click submit. It is done when the portal says so.
If you want the full sequence, how to apply to universities abroad step by step starts with exactly this kind of discipline. A grad school application completeness checker SaaS does not replace judgment, but it replaces the 2 a.m. panic of wondering whether you uploaded the right transcript everywhere. Run one, then get a full application audit at applicationreview.fyi before anything goes out. Ours is an application audit SaaS for students, built for exactly this pass.