Supervisors see the same handful of problems again and again, across every discipline and every cohort. The good news is that once you know what they are, every one of them is fully avoidable.
Starting to write before the research question is clear
Writing feels productive, so students often start drafting chapters before they have properly nailed down their research question. The result is usually a first chapter that has to be rewritten once the real question finally comes into focus. Before you write a single paragraph, write your research question in one sentence and get your supervisor to confirm it makes sense. Everything else should follow from that sentence, not the other way around.
Write your research question as one sentence and keep it visible while you work. Every paragraph you draft should trace back to it, or it belongs in a different section.
Treating the literature review as a summary exercise
As covered in more depth elsewhere on this blog, a literature review that simply lists what each author found, one after another, misses the entire point of the exercise. Group sources by theme, compare them directly, and use the review to justify your own research question rather than just proving you did the reading.
Ignoring your supervisor's early feedback
Some students receive early feedback, disagree with it privately, and quietly continue in their original direction anyway. This almost always resurfaces later, usually at a stage where changes are far more expensive to make. If you disagree with feedback, say so and discuss it directly. Supervisors would rather have that conversation early than discover a fundamental disagreement three chapters in.
Leaving data analysis until the last few weeks
Data analysis reliably takes longer than expected, especially the first time you use a particular statistical test or coding approach. Students who leave it until the final weeks often end up rushing the most important part of their entire thesis. Build in analysis time early, and run a small pilot analysis on a subset of your data as soon as it becomes available, so you catch problems while there is still time to fix them.
Formatting and referencing as an afterthought
Inconsistent formatting and referencing errors are entirely preventable, yet they remain one of the most common reasons for lost marks. Set up your citation manager and formatting template at the very start of your project, not the week before submission. A consistent format from day one costs almost nothing and prevents a frantic, error prone cleanup later.
Skipping a proper proofreading pass
By the time students reach their final draft, they have usually read it so many times that their brain automatically fills in missing words and skips over awkward phrasing. Reading the entire thesis aloud, or having someone else read it, catches errors that silent self review consistently misses. Give yourself at least a few full days between finishing your draft and your final proofread, so you can read it with genuinely fresh eyes.
None of these mistakes require exceptional talent to avoid. They require awareness, and a small amount of planning at the start of your project rather than a scramble at the end of it.