Job seekers perfect their resumes and compose thoughtful answers to common interview questions. But too often they’re timid about conducting an active salary negotiation, which is just as critical to cultivate a fruitful career. No matter how much you want a job, the experts say, you should not accept your first offer. Instead, you should learn to ask for more.

“Most salaries are negotiated,” explains Boston-based salary consultant Katie Donovan. “Salary negotiation is a game, and there are rules. Understand the rules, and you can make the most of them.” For starters, hiring managers typically leave at least 10% of what they can afford to pay off the table. They are ready for you to ask for more.

And you should: Earning 5% more could cover a month’s mortgage or that vacation you haven’t taken in years.

Actively negotiating also strengthens your career. “If you don’t push back, a company will know that you undervalue your resources,” Donovan tells individual clients and professional groups such as Harvard Business School alumni. “For the rest of your career at that company, your employer will think that you would have taken less—and that they overpaid you.”

Fill Out the Application With Care

If a job application asks for your desired salary or your current salary, don’t skip it. Simply enter $0. (These are required fields on most forms; you’ll have to write something to submit the application.) Any information you give about your former salary may diminish your bargaining power. An employer who knows you earned $50,000 will feel very confident offering you a 10% bump, or $55,000—and little more.

Donovan also advises her clients to ignore a written request for a credit check. “You’ve survived the past four years of economic hardship,” she says. “A credit check will only tell an employer how desperate you are for a job.” Employers once used these checks to screen applicants for banking jobs, but they are commonly used now as a way to judge responsibility. If the hirer presses you on this point, offer up references who can speak to your character. Ultimately, though, it’s not worth losing the job offer over what can seem like an invasion of privacy. If you have credit issues, explain your circumstances. The hiring manager will value your early explanation instead of discovering a problem when your report arrives.

Find Out The Going Rate For Your Position

Spend some time researching the going salary range for your job. Donovan likes Salary.com, but Glassdoor.com, Payscale.com and the New York Times Jobs page are also good sources of information. Each will prompt you to enter the job’s title, location, your education and experience levels to generate a bell curve. An attorney on the low end of the curve might earn $75,000, while someone on the high end earns $125,000 with the bell curve peaking at $100,000. You should aim for the highest salary on the curve—no matter your profession.

Be sure to consult your local and national industry organizations, too. Trade associations are excellent sources of information about earnings and hiring trends, including background about specific employers. Knowing what your position is worth will give you the confidence to suggest a new salary once the hiring manager opens the negotiation.

Express Enthusiasm – And Ask For More

Remember that a negotiation is simply a conversation. And it should be a friendly one, according to executive recruiter and author Leslie Ayers, whose coaching clients know her as The Job Search Guru. “Approach it knowing that salary is a business conversation,” she says. “A lot of people think it’s a conversation about your personal value or your worth, but it’s not—it’s about the company’s budget.” Remind yourself that a firm that wants to hire you wants you to be happy—not resentful because you feel underpaid.

When the employer offers you the job (on the phone), have notes ready. Take a deep breath and say: “Thank you very much. I’m interviewing for a range of jobs, and which one feels right to me is about much more than money. This job feels like a great opportunity. But the salary seems a little lower than what I thought it was going to be.” Follow immediately with, “Is there any way we can increase the base?” If you’re feeling very confident, you could add, “My research shows that the market value is 10% to 30% more.”

They’ll sigh and ask to consult with their colleagues for a couple of days. (They’re putting on a show, Donovan says.) They will usually return with a higher salary; if they don’t, they likely don’t have more to give. But now you know that you have not left money on the table. “The goal is not to win,” Ayers says. “The goal is to find a middle ground. But keep in mind: If you don’t ask, you don’t get.”

With the salary settled, if you feel confident, you can move on to the extras that make a good job even more pleasant: additional vacation, a higher bonus, telecommuting one day a week, stock options and health care coverage. Ask for industry memberships and conference costs to help build your network and skills.

“You already passed the test with your experience, capabilities and education. They know you’re good, or they wouldn’t be offering you the job,” Donovan says. “Now you have to show them that you know what you’re worth. When they feel they’ve been lucky to get someone really worthwhile, you’ll both feel like you’ve won.”