Here are some things that law professors should tell you so that, when you’re out in the real world, senior lawyers don’t have to worry about your professionalism:

1. Lawyers care about the written word.  So do law professors.  When you turn in a poorly proofread draft, we’ll form a not-very-flattering impression of your talent.  (We may like you, but we’ll still judge you.)  We will worry that you don’t know how to write well or, worse yet, that you do know how to write well but have decided that your time is more valuable than ours.  Making us parse your sentence fragments, your misspelled words, and a disorganized structure means that you didn’t take the time to check your work before handing it over to us. If you turned in this type of work to a lawyer at a firm, you would probably not get any more assignments, and your job would be in jeopardy.
2. Deadlines matter.  Clients don’t care that you worked hard on some other assignment and that you’re exhausted.  They don’t care that you’ve got the flu.  Law is a service industry, and the clients who are ill-served by lawyers who miss deadlines (or who wait until the last minute to finish their work) will find other lawyers to do their work in the future.
3. Yes, sometimes emergencies happen.  If you want us to form a better impression of your work ethic, ask for an extension before the date that something is due.  It’s best not to need an extension (see #2 above), but occasionally life interferes in some pretty awful ways.  If it looks as though you’re going to miss a deadline, the time to ask for help is well in advance.  (That’s why you don’t want to wait until the last minute to start a project–or to finish it.)  You never, ever want to be in the position of telling a senior lawyer who is counting on your work that it’s not going to get to her in time.

We want you to succeed.  The more professionally you behave in law school, the better your habits will be when you’re out in the “real world.”