Have you ever wondered if you should be getting paid more? If you haven't asked yourself that question, you should. Don't just assume that you're getting a fair salary. Instead, invest a little time in finding out what a fair pay scale is for your work. You may be surprised at what you learn.

Here are some questions to get you started, courtesy of the personal finance site GOBankingRates. And here is their full list of tell-tale signs that might mean you're underpaid.

1. Are others in your company making more for similar work?

It may or may not be easy to find out what your colleagues are being paid, but if you can get it, that information is always very enlightening. I remember finding out once that someone else was literally making twice what I was for the same work.

How did I use that information? I didn't march into my boss's office and complain that someone less experienced was making more than me. Instead, I came up with a reasonable rationale for doubling my own pay that didn't mention my colleague at all, and it worked. Asking for a raise based on someone else's salary makes you seem petty and envious instead of what you are: someone who knows the value of your own work.

2. What are people at other companies earning for doing your job?

Looking at ads for jobs with the same kind of skills and experience that you have should give you some insight into what you should be making. Asking around at industry trade shows and conferences can also give you valuable data. You can get lots of general information about what people doing jobs similar to yours are earning by doing a little online research. Try checking out Comparably.com for example. The Bureau of Labor Statistics also offers detailed data on pay by occupation and geographic location.

Asking around at other companies may also help you land some job offers. If that happens, you have a powerful tool to use in salary negotiations.

3. Have you recently learned new skills?

Whether you've gotten on-the-job training, taken on new responsibilities, or taken courses to upgrade your skills, the fact is you've increased your skill set. That makes you more valuable to your employer, and that increased value should be reflected in your paycheck.

Your employer may not take the initiative to increase your pay because of your new skills. You will likely have to make your case to your boss that your new skill set is a good reason for an increase. Try and suggest ways using your new skills to save the company money or increase revenues.

4. What is your company offering when it hires new people for jobs similar to yours?

If your employer has any open positions similar to yours, now is your chance to gather some valuable intel. Check out any job ads your employer publishes or posts for those open positions. Chances are, they'll mention a salary range, which should give you an idea of what your company would offer to a new hire with skills like yours. Use that information to help make a case for why you should get an increase.