Filling out your UCAS application should be treated as filling out any other application. If your application has your name spelt wrong, or your phone number is filled out incorrectly, you are not giving yourself the best chance of being accepted. You must take time to ensure every section on UCAS is filled out correctly; anything which is incorrect will most likely harm your chance of application. You have the chance to fill it out and review as many times as you need, so get someone else to check everything over. You might think you will not get anything wrong, but in some cases it is easier to make a mistake on something so obvious.
When filling out your qualifications and examination results you mustn’t be tempted to alter anything. Not only will your predicted grades appear in your reference, but they will also be confirmed by UCAS. Providing false information will only harm your application, and will not benefit you in any way. Take extra time in ensuring that the dates of qualifications are correct, and that the subjects and schools are spelt correctly. Having an A* at GCSE English Language is a really good accomplishment, but it loses its shine if you spell Language incorrectly!
It is important that you include your correct contact information. Throughout the application process it may be necessary for a university to contact you. So use a telephone number people answer, use an email which you check regularly, if you live at school during term time, and include both your school and home address in case you are contacted in or out of term time.