On average, job seekers look for jobs on up to 16 different sources. That's not a typo.

It can quickly become all-encompassing for hiring managers to ensure job listings have coverage on all the sites where your ideal job seekers may be looking for work. Plus, each site performs differently, and managing each campaign closely is a must to ensure you aren't wasting money on inefficient spend.

In order to source effectively, you need to post to the right job boards for your specific role, industry and location. Some boards will be free and others will be paid.

Research and trial-and-error will tell you over time which boards are best for your specific roles. Better yet, hiring software that enables you to post across multiple job sites at once for each role ensures that you are using staff time and resources as efficiently as possible.

Hopefully, we can help you with some of that hard work. Here are five tricks you can use to find job seekers wherever they're looking, without spreading yourself too thin or wasting too much money:

1. Optimize campaign spend closely.

If you're using paid job boards, you need to closely watch your campaigns on each site to see which are driving the best cost per application.

Checking your spend and application metrics for specific job listings and changing bids daily will give you the best return on your investment, and will ensure you aren't wasting money on attracting a large volume of clicks but not qualified applicants.

Over time, you'll want to shift your budget to the best-performing job boards for each role and eliminate sourcing methods that provide no or low return on investment.

2. Focus on reaching passive candidates.

Consider how your brand can reach passive candidates who may not be regularly searching your site or job boards for a new position. These invisible candidates are the hardest to find--but are often the most qualified hires.

Leveraging references provided by your existing applicant pool can be an effective method of sourcing passive candidates. In addition, consider implementing an internal referral system that incentivizes your existing employees to recommend previous colleagues or peers to open roles.

If you know what your cost per hire is, wouldn't you rather pay that money to an employee than an outside service?

3. Create your own talent network.

Don't discount industry referrals. Consider which peers in your industry may be able to recommend quality candidates who applied for positions they ended up filling at their companies.

Reach out to employers in your industry and build a reciprocal relationship in which you both refer candidates who may be a good match. If creating your own network sounds difficult, you may want to talk to your applicant tracking system provider.

Most hiring platforms don't come with their own talent network. Still, you may find one with its own network that you can plug into as part of being a customer.

4. Consider social media recruiting.

There is a very good chance that your target candidates are on social networks.

According to Pew Research Center's 2016 social media study, 68 percent of all US adults use Facebook. Narrow the age range to between 18 and 29, and that number rises to 88 percent.

If you're hiring for more white collar roles, you don't want to ignore LinkedIn. 29 percent of online adults are on the professional networking site.

Posting your roles to social networks isn't as simple as a "post it and forget it" strategy. Social platforms are built to drive conversations, so you should actively manage any that spring up around your job post.

Replying to any comments or questions quickly provides a better experience for the candidate, and sends a signal to job seekers that you are invested in the hiring process--and that they can expect good communication from your company should they decide to apply.

5. Look into solution providers.

Sourcing can be so time consuming that it takes away valuable time spent building relationships with best candidates.

Consider partnering with a solutions provider who can automate the sourcing processes above. Ideally, your applicant tracking system can automate as much as possible, so you can free up more time while still maximizing your ability to find the best candidates.