The ability to negotiate is a key skill in business, even more so when accepting a job offer or getting promoted to a new position. However, chances are you probably didn't ask for enough money.

According to research, fewer than a third of people successfully negotiate their salary to increase their earnings. The majority simply aren't comfortable enough with asking for a pay raise.

The research states that, overall, the majority of people (84 percent) confident enough to ask for more pay were successful in getting it. And about a fifth of those who negotiated were rewarded with a significant pay increase somewhere between 11 to 20 percent.

While negotiating for more pay can be downright stressful, if the conditions and approach are right, it's still the best and simplest route to increasing your income. Here are four ways to do it well, so you don't potentially leave money on the table.

1. Prove your worth 

When you actually prove you deserve that raise, and explain how your work or skills lead to raising revenue or saving the company money, you'll most likely get the attention of those in the position of increasing your pay. The key is making a case and putting in writing the clear and compelling reasons for why you deserve a raise.

2. Know your worth

Find comparable salary ranges for your industry, location, position, and experience using resources like Indeed or LinkedIn Salary. 

3. Prep your boss in advance

Rather than waiting till the 11th hour, let your boss know a good six months in advance that you want a raise and agree to what targets you need to hit to make that happen. The approach here is key. You don't want to put your boss on the defensive. Be specific on goals and targets by getting on the same page, and by putting it in writing. Finally, when you get near the six-month mark, circle back with your boss to show what you've accomplished, and then schedule a meeting to discuss the raise.

4. Justify your worth

Come to the negotiating table with a specific number in mind and be prepared to justify why you're worth what you're worth. Otherwise, a more experienced hiring manager will control the negotiation to his or her outcome, not yours. This is also important to help you know how you'll respond if your boss objects to the raise in question. Then, put the focus back on the value that you currently bring, or will bring, to the business.