No matter how extensive your experience and skills, a new job hunt is always stressful. If you’re competing for a wildly sought-after position, the margins of error are tiny; you feel like you must ace every interview and testing round.

With all that pressure bearing down on you, it’s easy to make mistakes. Some of these are potentially forgivable; answering “I don’t know” to a technical question during an interview, for example, won’t always wreck your changes of landing the gig (depending on the question, of course, and how you follow up on it). But other things will kill your momentum absolutely dead. Let’s examine some of those:

Neglecting Your Cover Letter (Or Worse, Your Résumé)

More and more companies rely on browser-based job applications to screen candidates. If you’re hunting for a job, you’ve no doubt completed your fair share: page after page of blank fields to fill in, from your name to your education and skills.

These applications often ask you to upload your résumé and/or cover letter, with the cover letter portion sometimes presented as “optional.” That’s a trick—you should always consider it mandatory to submit a cover letter.

Beyond these application systems, one of the worst things you can do when seeking a new job is neglecting to customize your résumé and cover letter to each position you want. The tech industry’s low unemployment rate might lull you into thinking that you can send a company a generic résumé and receive a call-back; or you might think that résumés and cover letters are horribly outdated concepts, documents that hiring managers and recruiters barely look at.

But the reality is that hiring managers, recruiters, and teams all examine the résumés and cover letters of potential team members—and they’ll know instantly if the documents are a weak and un-targeted effort. When in doubt, spend as much time polishing your résumé and cover letter as possible. Make sure the message conveyed by your materials is on-point and laser-focused on the position you want.

Getting Too Creative

Unless you’re a graphic designer applying to a firm that’s known for its eccentricity, there is absolutely no reason to get too creative with your résumé, or show up for the job interview in costume.

Sure, some candidates have succeeded by creating CVs that look like Amazon pages or Instagram posts, or even 3D-printing their head and leaving it for an interviewer. But the screening software utilized by many companies can’t read “uniquely” formatted résumés, and trying a stunt during your interview might seem weird instead of intriguing, depending on the interviewer’s personality and frame of mind.

When in doubt, try to color within the lines when it comes to the application process. Once you’re sitting in front of the interviewer, you can describe your creative approaches to successful projects, for instance—but save any “arty” impulses for your personal pursuits.

Getting Too Pushy

You sent in your application for a job you really want, and never heard anything back. After waiting a few weeks, you shot an email to the recruiter, who didn’t bother to respond back. What’s your next step?

Many tech pros would probably assume they didn’t get the job, and move onto the next application. Others might send another email, or even phone the recruiter or hiring manager, before giving up. Those are all reasonable responses.

Whatever you choose to do in the face of silence, though, there’s one behavior you definitely shouldn’t engage in: Obsessively phoning or emailing about the gig. Blowing up a recruiter or hiring manager’s inbox or voicemail is the surest way to ensure you’ll end up blackballed by that company for good, even if your skills align with the current or future positions on offer.

You might think that constant calling is doing everyone a favor (you’re the best person for the job, after all), but it’s really making you come off like this:

Don’t be that dude.

Lying About Your Skills

It might be tempting to “fudge” your CV a bit. But embellishing your skills and experience will inevitably blow back on you. A hiring manager or recruiter might discover your duplicitousness pretty much immediately, via simple scan of social media; or your future co-workers will find out when you’re not really capable of doing what you claimed on your application materials. And keep in mind: There’s no anger quite like the anger of a team that’s discovered a new member can’t do the job they were hired to do.  

Not Doing Your Prep

Have you built out your network of contacts (i.e., professional colleagues, former co-workers, etc.)? Is your social media scrubbed of anything that potentially makes you look bad? Have you scanned (and re-scanned, and re-re-scanned) your résumé, cover letter, and other materials for typos and inaccurate information?

The point is, you can’t just spontaneously plunge into a new job search. Make sure that the people who need are alerted, that your documents and online profiles are up-to-date, and you have an idea of what you want to do (and for how much). Otherwise, you could very well end up spinning your wheels.