1. Not having a realistic idea of what you're qualified for. Too many college students come out of school without understanding what jobs they have a realistic shot at doing. As a result, they often shoot too high and then get frustrated when they don't get interviews. Make sure to talk to people in the field you'd like to enter to understand how best to frame your candidacy and what jobs to target first.
2. Including loads of details about your course work on your résumé. Recent grads spend the first half of their résumé on education, notes on coursework and honors. But what you really want to play up is work experience, not details about your courses. A hiring manager is likely to spend only 20 seconds on the initial scan of your résumé and what she needs to see in that time is work experience directly relevant to what she's hiring for, not a list of college courses you took.
3. Having a lengthy, multi-page résumé. When you're right out of school, you rarely have enough work experience to justify a résumé longer than one page – and it can make you come across as self-important or unable to edit. Stick to a single page if your experience is limited.
4. Not reaching out to your network. You might feel silly reaching out to your parents' friend about a job, like they keep pushing you to, but using your network in a job search is both normal and often extraordinarily helpful. People in your network can connect you with jobs, refer you to hiring managers and give you valuable information about your field. If you ignore them because you're shy or not convinced it will absolutely work, you'll forfeit a tool that can be one of the most helpful in a job search.
5. Searching for your dream job. You're unlikely to be qualified for your dream job straight out of school, and holding out for one will make you lose out on other opportunities. More importantly, you really can't know whether something is a dream job or not until you're working there. While you might think that you might love doing that work for that company, it might turn out that the boss is a nightmare, or your co-workers are horrible, or the company makes you bring in a doctor's note every time you have a cold, or your work load is so unreasonably high that you end up having panic attacks every morning. It's smarter to look for a job you can do well and with which you'll be reasonably happy.
6. Not helping employers understand how your experience relates to their needs. New grads often come out of school with a strong package of skills but not much understanding of how to frame those qualifications in terms that will resonate with employers. The language and framework that worked in academia may not work with employers, so this piece of the transition from campus to work can be a hard one.
7. Being overly formal. Some new grads expect the work world to be more formal than it often is, and this culture disconnect can show in everything from overly stiff cover letters, to unnecessarily formal emails to co-workers, to feeling awkward calling their much older boss by a first name. They can make a better impression by realizing that employers and co-workers – even if many decades older – are regular people just like they are and generally appreciate being treated that way. On the other hand…
8. Not being formal enough. While new grads shouldn't be excessively formal, they shouldn't go to the other extreme either. Most offices expect a certain degree of decorum: no slang or text-speak when talking with your boss or a client, no bare feet in meetings, and no treating the receptionist like you just met her in a bar, among other things.
Alison Green writes the popular Ask a Manager blog, where she dispenses advice on career, job search, and management issues. She's also the co-author of Managing to Change the World: The Nonprofit Manager's Guide to Getting Results, and former chief of staff of a successful nonprofit organization, where she oversaw day-to-day staff management, hiring, firing, and employee development.