Having been on the receiving end a fair few times, a few tips: One, if at all possible, find out the name of the person you're applying to, and address a brief covering note to them by name. ('Dear Sir/Madam' just says 'I'm so keen to work for you I can't even be bothered to find out who you are.') Two, the key word there is 'brief'. Three, spell their name correctly. Oh, and for a fourth that, along with the others, will put you ahead of 90% of other applicants, run a spell check on your brief note and CV, following up with a careful look for errors the checker won't spot (their/there/they're and the like).