You're in Trouble if You Ignore These 5 Applicant Red Flags Bad hires can damage your reputation along with your bottom line.

I've made every hiring mistake in the book. Everything I'm warning against here, I've already done. Which just goes to prove I'm one of you.

Most entrepreneurs learn hard lessons about hiring the right people only after they've hired the wrong ones. Even after realizing the mistake, business owners still can be prone to errors in judgment. Whether you're an established entrepreneur who could use a refresher or a newer entrant to business ownership, it's worth knowing these five characteristics of potentially disastrous hires.

1. They're job hoppers.

People who hop from job to job will hop away from you sooner or later -- and much likely, it's sooner. In this case, the past predicts the future. Every job-hopping applicant I've interviewed has provided an excellent reason for leaving every past employer. Job hoppers are incredibly effective at explaining their rationale.

While some industries and skill positions defy universal application of my unwritten rule, I look for people with stable, long-term employment at one company in their professional careers. To my way of thinking, that's five or more years. Younger candidates get a bit more leeway and a lower threshold. The most important factor is a candidate's ability to develop a relationship with a company over an extended period.

Related: This is What You Get When You Ignore 'Quality of Hire'

2. They can't tell you what they did at their last job.

Watch out if the candidate's current or previous role was amorphous, with equally unclear achievements. Entrepreneurial companies must focus on people who can increase revenue, build things or get things done. Doers might have roles not tied to revenue or products, but they should be able to explain tangible results.

While I look for stable employment within a company, I'm also aware that people with ambiguous roles can hide at larger companies -- sometimes for years. Candidates should explain in clear language what they actually did and how it specifically helped the company. Think of the consultant scene in "Office Space" and the question posed to each employee: "What would you say you do here?"

Related: What Really Happens When You Hire the Wrong Candidate

3. Their names return negative search results.

It's an easy call if a Google search of the candidate's name reveals he or she has been sued for skydiving naked off the Empire State Building. In real life, though, it's rarely that simple. At minimum, vet all candidates with an online search and a thorough scan of social media platforms -- within legal limits, of course.

4. Their references give less-than-stellar feedback.

People generally don't want to say bad things about others. During reference checks, asking a variety of subtle but probing questions could save your company money and embarrassment (or worse). I've noticed a tendency to downplay this phase of the hiring process. It's become a check in a box on a form. Legitimate due diligence demands more. It's so rare today to get any sort of negative feedback that I'm concerned when a reference contact has anything even slightly unflattering to say about a job candidate.

Related: When Hiring, Give Negative References More Weight

5. They talk negatively about others.

This one's a dead giveaway. When candidates speak negatively about a current or former employer, colleague or acquaintance, they're giving you valuable insight into their very characters. People who put down others will be more inclined to bring that same negative philosophy to their role, your company and your team. It is not worth the risk to hire these individuals, no matter how impressive their credentials.

Here's another red flag that didn't make the Top 5 list but also speaks to character or fit: They don't do the basics. These candidates know little to nothing about your company, are rude to or dismissive of your front-office reception staff and forget to follow up the interview with a thank-you note.

Entrepreneurs necessarily focus on getting things done quickly. In hiring terms, that can be a huge mistake. Remember the saying: "Hire slow, fire fast."