You're about to begin an internship, become a summer associate, or start your first job. More than anything, you want to make a positive first impression, one that will mark you as a consummate professional. You know it's critical to avoid mistakes that could damage your reputation or harm your employer. But it's tough figuring out what it is you don't know. Not to worry. Mary Crane has worked extensively with young professionals and their employers to develop a list of the 100 most important things you need to know as you enter the world of work--crucial information in "easy to absorb," almost tweetable chunks. You can't know everything. But tackle the "100 Things You Need to Know" before you start work, and you will successfully launch your career.