Firing under-performing employees can be incredibly costly (one estimate puts the price tag as high as $840,00 for a mid-level manager), but keeping around mediocre hires is seriously expensive too (another expert suggests they suck 15X their salary out of your business each year).

Obviously, the best course of action then is to hire the right person in the first place. How do you do that? Advice abounds, but rarely is it as specific and useful as a long recent blog post from OkDork CEO Noah Kagan. In it he shares all the lessons he learned reviewing over 10,000 applications as he built out his team to over 40 people.

The complete post is well worth a read if your hiring skills could use a polish, but here are a few of Kagan's ideas to get you started.

1. Most hiring managers have no idea what they really want out of a hire.

But wait, you probably protest. I know exactly the position I'm looking to fill, the number of years of experience a candidate should have, and the skills they need to succeed. So I'm all set to start writing that job description, right?

Far from it, insists Kagan. To land the best talent, you need to know not only a broad-strokes understanding of who you want to hire, but also the nitty gritty of exactly what you want him or her to accomplish. "Otherwise, you're setting your future team member (and yourself) up for failure," Kagan believes.

So before you craft your job description, get brainstorming. "The first step in my hiring process is to write down a list of tasks I need the new hire to do," he instructs. "You don't need an exhaustive A-to-Z list of every little thing. You just need to clearly reflect how this team member can help your business -- and what tasks you need them to handle."

The result should be specific tasks like "write 1-2 blog posts per week," not empty recruiting speak like "handle editorial tasks as needed."

2. Average job descriptions attract average candidates.

Once you know exactly what you want, it's time to sit down and write a job description. You might think of this as a basic administrative chore, but according to Kagan, it's actually more of a literary exercise. The quality of the job description is directly related to the quality of the candidate who replies. "If you want 'A' players applying, you need an 'A' sales pitch," he believes.

What counts as a great job description? First, expect to spend hours, not minutes, on the task. Then, make sure you include these five elements:

  • Start with a story. Humans can't resist a good tale, so this is a great initial hook.
  • What's the role. What you need this person to accomplish written in plain, punchy English.
  • What's in it for the applicant. This doesn't just mean money!
  • Skills/Requirements. This should cover both technical requirements and personality traits necessary for success (and happiness) at your company.

  • Tasks. Setting a few simple tasks for applicants in your description weeds out the under-qualified and the lazy, saving you time and frustration (more on this below).

3. A tiny amount of tech can save you massive amounts of time (and frustration).

When Kagan was trying to hire an editor recently, he set applicants three incredible simple tasks: email their response to a job-specific email address, include a link to their LinkedIn profile, and pick out four grammar and spelling mistakes in the ad. A whopping 35 percent couldn't even manage to clear this low hurdle.

Weeding out slackers like these can obviously save you a ton of time and frustration. Tech can help. Kagan didn't manually chuck each weak application. He let Google do it for him, by using Google Forms and Canned Responses to automatically check which candidates managed the set tasks and then send those that did a form email inviting them to complete a quick challenge to make it to the next round.

Want to steal his idea? He walks interested bosses through it step by step in the post, along with offering a whole lot more hiring wisdom.

Share your own hard-won wisdom: what's your best hiring hack?