Your letter of application is very important: it is how you address a particular company and particular vacancy in a very personal way. You state in it why you are applying and what you expect. Each letter of application is different. And that is also important because those minor details can make a real difference.
Tips from Manpower
Keep it short: a good letter of application is written in a direct and simple way, in short, clear sentences.
Write correctly: language and typing mistakes in a letter of application are immediately penalised. A letter of application is also personal: avoid standard formulas and adapt the style of your letter. Write in a positive, dynamic and future-oriented way.
Write in a personal way: (if possible) address a person and not a department. A person who feels addressed will pay much greater attention to your application.
Be confident: write in the present tense. Write affirmatively: in that way you show the employer that you are confident.
Write positively: a letter of application must be focused on solutions and not raise problems. Use words that create a positive feeling and are action focussed.
Be committed: a person who is not convinced cannot convince other people. You will only excite interest in others by being 100% committed and motivated.
Be direct: to draw the attention, your letter of application must be targeted. Your arguments must be clear and concrete but not exaggerated. So do not use hollow words or long sentences to make your letter needlessly complicated.
Be specific: write each letter of application specifically for a particular job vacancy and answer the requirements set as well as possible. Avoid repetition.