Foreign applicants must get their CV, covering letter and application forms checked by native English speakers before applying to companies. Even the smallest mistake may result in your applications being rejected, and it can be very hard to produce a perfect application if you are not a native English speaker.
Articles
[Edit]Remember that articles should fit before a noun in most sentences. For example, "I am a student at The University of Leicester" and "I work in a restaurant".
Prepositions
[Edit]Prepositions are notoriously difficult in every language and there are no set rules for mastering them other than to practice and learn them. If you use the wrong preposition, it will be very apparent to your reader. Always use a dictionary to check which preposition the verb takes.
