In its first year of business, Hired organized thousands of developer interviews for companies trying to fill spots. It quickly became clear why some companies couldn’t hire. “Ninety percent of companies are bad at hiring, but it’s particularly bad among seed stage companies and first time founders,” says founder Matt Mickiewicz. Here are the most common hiring mistakes made by employers on Hired:

Too many twentysomething founders look for employees just like themselves. “So you discriminate against anyone who is in their 30s or 40s or has a family,” says Mickiewicz. “But the most talented and experienced people will be in their 30s and 40s. I know one well-known startup who has been trying to fill a role for over four months, and has gone through two dozen candidates, simply because the founder mandates 80-hour workweeks.”

Founders typically look for candidates who have a similar educational background to themselves and live within 25 miles of their office. A CEO with a Stanford CS degree will often look down on anybody who doesn’t, but this seriously limits the talent pool available to his startup. “We look a lot outside Silicon Valley,” says Mickiewicz on recruiting for Hired itself. “There are really talented people who don’t live on the coast and there’s a lot less competition for that talent.”

Another typical form of hiring self-sabotage is to concentrate on candidates from well-known companies like Google, Facebook, or Apple. “Don’t just cherry-pick the Google engineers and the Stanford grads to work at your ‘Uber for Laundry,'” says Mickiewicz. “Hiring Google engineers is generally a really bad idea. If you work at Google you have access to an entire set of tools and technologies that you won’t have in a smaller startup environment.” Hired has also found that Google engineers are three times more likely than average to reject interview requests, simply because few companies are willing to match a Googler’s existing salary.

On the other hand, startup CEOs tends to be prejudiced against developers who work for less cutting-edge large companies, like Dell, Accenture, or Salesforce. Mickiewicz points out that Uber’s CTO was hired from VMware.

Too many interviewers still rely on puzzles and programming trivia questions. Google stopped asking puzzle questions in interviews when it found that the fact that a candidate could calculate how many golf balls fit into a plane had no bearing on whether they could actually do the job.

Viewing the interview as a combat sport is another common pitfall. “Asking an engineer to architect Google Maps on the whiteboard when they work for a car-sharing startup,” Mickiewicz says, “just because the CTO worked on Google Maps. It becomes like a battle of wits. The CTO versus the applicants: Who’s smarter?”