Although your CV might contain all the requisite information, it shows indifference if you ignore an application form. And, it should go without saying, make sure you read and comply with all the instructions. Recruiters often complain that candidates neglect to list all their academic results. Watch out for the firms that consider A-Level and GCSE results as well as university grades. They are looking for consistency as well as competence.
Referees are important.
Make sure your academic or work referees are going to be highly favourable. It's surprising how many lukewarm references are given, because an applicant has not primed a referee. Let important information stand out. Bullet-point where possible. Spelling mistakes, unfortunately, rob many applicants of an interview.