When completing a job application or writing a cover letter for your resume, keep it as concise as you can. Use short sentences and limit the length of your paragraphs. Try not to go over one side of A4 paper. Only include pertinent information and don't waffle.
Cover All Bases
Make sure that you deal with every aspect of the job description and personal specification and provide examples of how your experience makes you the best candidate for the job. Deal with each point briefly, but with confidence and authority.
Your supporting statement is your opportunity to sell yourself. Your experience and qualifications are one thing, but it's here that a prospective employer gets a real flavour of who you are. Concentrate on your introduction. A snappy first paragraph can really make you stand out. You can win or lose an interview on what you write here.