If you check your paper but still miss mistakes, the problem may be that your checking is too general. Simply rereading from the beginning often recreates the same assumptions that produced the error. Effective checking looks for specific failure types rather than asking vaguely whether everything seems fine.
Build a short sequence around your own error history. Check unanswered parts first, then signs or units, copied numbers, command words, final-answer form, and any question where the working changed direction. For calculations, use an inverse or estimation where possible; for writing, check one feature at a time rather than trying to notice grammar, spelling, meaning, and punctuation simultaneously.
Use the Examinations & Assessment Hub for paper routines, and I Keep Making Careless Mistakes in Exams — What Should I Do? to build the checking sequence around your actual error pattern.