The most stupid mistake I made during a job-hunting process was making mistakes on contact information. During my undergrad a professor in my university was looking for students to recommend for a nice Ph.D. program. I wanted to polish my resume, so I asked for my friend’s template. He instead gave me his full resume. I updated the resume with my name and experiences but left a wrong phone number. The professor happened to be old school and relied on phone calls. After a few weeks I met the professor, and he told me he tried to contact me for the opportunity, but the phone number wouldn’t work. He had to choose someone else even though he thought I was the perfect candidate, and I lost a good opportunity for a nice Ph.D. program. The lesson here is that during the job search, make sure to double check details on your resume and contact information.
I think the biggest mistake I made while job-hunting (this was probably like 8 years ago) was using the same cover letter for several job applications and just changing the name of the company. Back then, I thought the secret of getting an interview was just a matter of numbers and the more applications I got out the door the better off I would be. So I created a generic cover letter, and I only changed the name of the company. What eventually happened is that I ended up mixing names of companies and sending wrong cover letters. In one of those attempts I actually got a reply back from HR stating that they had liked my profile but given my lack of attention to details they weren't going to take my application into consideration. That experience was painful but necessary, I learned that there are no shortcuts when it comes to job hunting and started focusing on jobs that I really liked and putting effort to building custom applications to those jobs.
Yes, I’ve definitely made mistakes in the job-hunting process. One of the biggest ones was relying too much on "quick apply" or "easy apply" options without taking the time to tailor my resume or write a cover letter that showed genuine interest in the company. I thought applying to as many positions as possible would increase my chances, but in reality, I was just sending out generic applications.
The consequence was that I wasted a lot of time on quantity over quality. I realized that focusing on fewer applications and customizing each one to the role and company would have been much more effective. It was a valuable lesson in the importance of being intentional with the job search process.