Creating a resume explaining your objective, your skills, your education and your work experience is a crucial component of professional development for all individuals. Aside from an email, a brief telephone call or an in-person visit, your resume will represent the first impression you make on a potential employer.

Right now, there are approximately nine job seekers per job opening, making the current job market extremely competitive, particularly in certain fields. While an excellent resume has the power to put you on the short-list of potential employees that will actually receive a request for an interview, a poor resume can just as easily write you off as a viable option, even if your actual job skills greatly outpace your resume writing ability.

Although it’s relatively easy to understand how to format and compose a resume, avoiding common pitfalls can be more difficult. Here are five resume mistakes that will instantly leave a poor impression on potential employers:

1. Too Long or Too Short

In the current economic climate, employers can expect to receive dozens if not hundreds or even thousands of resumes seeking a single job opening. As you can imagine, properly evaluating such an enormous pile of resumes is a time-consuming task that easily becomes frustrating when some of the resumes ramble on for pages and pages, boasting about every life accomplishment while failing to tell the employer what they really need to know.

Restrict your resume to a single page if even remotely possible. Depending on your relevant work and education history, it may be necessary to use two or even three pages, so long as those pages are filled exclusively with information relevant to the open position. If you’re applying for a position as a senior IT manager, for example, mentioning that you worked at Burger King when you were 17 will only make your resume longer, not better.

At the same time, a resume that was obviously created in five minutes and barely tells the employer who you are will be dismissed even faster. Spend only as much space as you need to tell the employer exactly why there couldn’t be a better candidate for the job than you.

2. Failing to Adhere to the Employer’s Instructions

If you can’t be bothered to follow the employer’s instructions when you’re submitting your resume, how could they comfortably trust you to follow instructions when you’re on the job? Failing to meet the employer’s exact submission requirements is a great way to instantly send your resume to the “not even a chance” pile.

The key is to read the job posting carefully. If the employer wants a one-page cover sheet included with your resume, don’t send a two-page cover sheet or no cover sheet at all. If the employer doesn’t want any phone calls regarding the job opening, respect her wishes and communicate via email. If the employer wants the materials submitted in the body of an email, don’t add them as an attachment.

You may think you’re being clever by ignoring the employer’s instructions and giving them something that you assume they’ll appreciate more, but in reality you’re just telling them you have a hard time with directions.

3. Only Saying What You Did, not How You Did It

It’s great that you have a steady history of employment at a variety of respected companies, but that doesn’t tell your potential future employer much about how you actually performed your job on a day to day basis. Your resume should explain specifically why you were an asset in your former position, with lines such as “Maintained agreements with shipping providers to reduce overhead costs by 20%.”

Ideally, your past work accomplishments should directly support your argument that you’ll be a perfect fit for the open position. If you’re applying for a sales position, for example, explain how many vehicles you sold at your former auto dealership, not just that you worked there for three years.

4. Citing Generic Skills Instead of Specific Ones

Anyone can say that they have “excellent leadership abilities,” “impeccable organizational skills” or that they’re “comfortable working alone or in a group.” Employers are looking for specific skills that apply directly to the job, and that show real knowledge of the applicable industry when they’re presented on a resume.

Start by reading the list of qualifications the employer is looking for, but pay even closer attention to the list of tasks for which you’ll be responsible if hired. Can you explain how and why you’ll be capable of performing those tasks using industry terminology (but not wordy jargon) that your potential employer will instantly recognize?

5. Lying

The last thing you want to include in your professional resume is a lie, even if it’s a white lie or one so minor that you’d never expect the employer to notice anything is amiss. The reality is that modern employers actually have plenty of ways to detect whether something is amiss, ranging from old-school methods such as calling your references to more modern tools such as social media and search engines. Depending on your history, you may have an extensive online presence without even realizing it (Google your name now if you’re skeptical).

Regardless of the reasoning behind your lie, even if it’s made purely with good intentions, most employers will instantly rule you out for the position, believing that you can’t be trusted. Keep the information accurate, and squeeze in extra value by ensuring perfect formatting, aesthetics and readability rather than exaggerating your credentials.