You've been working at the same company for a while, and you plan to ask for a raise. But before you do, you really want to know what other people with the same or similar jobs are making, and whether their salaries are higher than yours. Or maybe you want to hire a key employee away from a competitor--or avoid having a valued employee of your own lured away by a higher salary.

Whatever the reason, you really want to know what somebody else is making. And you know it's not a question you can easily ask. Are there other ways to gain this crucial information? Yes, it turns out. The personal finance site GOBankingRates just published a guide to learning about other people's salaries. Some will give you a range that the person's salary likely falls into, others might give you the precise information you're seeking. You can find the full guide here. These are some of the best tips:

1. Do some online research.

This should probably be the first step in your quest to find out someone's salary. Begin with Glassdoor and PayScale, two sites that will give you a good idea of the range people are earning for a specific job in your industry. Because people post their actual salaries to Glassdoor, you may be able to find out roughly what another company is paying for a specific job. If you're very lucky, the person you're wondering about might actually have revealed his or her salary on Glassdoor (the site encourages people seeking information to also share some). If you can recognize your target by job title or by that person's description of the work in a review, you could get precisely the info you need.

If not, don't stop there. Try the Bureau of Labor Statistics which provides general estimates for salaries in various industries (keep in mind there can be wide geographic variations--if you're in a high cost of living area such as New York City or Silicon Valley, the BLS salaries might look low to you). 

GOBankingRates also suggests reaching out to your alma mater if there are graduates of working in the industry or role you're curious about. Many of these offices seek salary information from graduates, and you may be able to get some useful data back.

Finally, don't forget to check job listings for the organization in question. That will at least tell you what prospective job candidates are being told about salary ranges.

2. Check public records.

If you want to know the salary of someone who works for non-profit organization or a government (including local government), then the salary for that position should be a matter of public record. For federal employees, try the U.S. Office of Personnel Management. For municipal employees it can be trickier, but the town or locality is supposed to provide a salary report. For nonprofits, check GuideStar

Public companies must also disclose top officers' compensation. So, if you're trying to find out what the CEO or other top execs make at a public company, that information should be readily available on financial websites. 

3. Ask your mentor.

If you have a mentor, whether inside your company or not, he or she should have a broader view of what others in your organization or industry are earning. (So will a VC, if you're working with one.) Your mentor might even know the actual salary of the person you're curious about. He or she may be unwilling or unable to divulge that information, but be specific about what you're trying to accomplish. For instance: "I'm planning to ask for a raise, and it would help me to know whether I'm earning less or more than others in similar positions here." Your mentor should be able to provide some guidance.

4. Ask a former colleague.

Someone who's left your company (or another company that you're curious about) will likely be much more willing to share salary information--and all kinds of other information, as well. So, invite one or more former employees out for coffee or lunch or after-work drinks. You may be surprised at how much you can learn this way.

5. Offer to trade information.

Sometimes your only good option is to ask someone directly what his or her salary is. As GOBankingRates points out, there are a lot of risks to this. But if you decide to do it, the best approach is to offer to exchange information. Begin by saying you have an awkward question to ask--it helps to acknowledge up-front this is a difficult subject and that you'll understand if the other person chooses not to answer. Then explain you need to benchmark your salary because of an upcoming negotiation or because you're evaluating a competing offer, or looking to hire. Offer to share your own salary information, or if you're looking to hire, offer to share information on what you've paid in the past for this job. 

The other person may be willing to reveal a specific salary, or perhaps a salary range he or she falls into. Or he or she might simply say no. If that happens, don't get upset. Thank your colleague for taking the time to talk with you, and leave the door open for a future conversation, in case the person has a change of heart and wants to talk about salaries in the future. You never know, he or she just might.