I am filling out an online job application for a law firm and there is a 'box' for a covering letter. As it's obvious the position I am applying for and who I am, should I start with the usual paragraph of introducing myself and what job I am applying for, or can I go straight into the main part of the letter i.e. why I am perfect for the job.  There is a limited word count, so I don't want to waste words unnecessarily. Any thoughts?