Credit is a gift, not a given. Mistakes can be costly; here's how to avoid missteps.

Leave breathing room. "Stay under 25 percent of your available credit line," says Anne Marie Kehoe, adjunct professor of financial planning at LIU Post in Brookville. Lenders don't want to see that you've eaten up every dollar you could get your hands on.

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Timeliness counts. "Paying late is the worst thing you can do besides not paying at all," says David Bendix, president of The Bendix Financial Group in Garden City. "Late payments look bad on your credit report; it also gives lenders the opportunity to attach more fees." Payment history makes up about 35 percent of your credit score, says Nancy Orlando, senior vice president of credit at Teachers Federal Credit Union in Hauppauge.

Say yes: It's not smart to avoid credit. "If you have no credit, lenders don't know if you can deal with debt," says Jeff Hindenach, editor of NextAdvisor.com, a financial services comparison site.

Fix credit carefully: Don't cancel all your cards. "This drops your credit score, because it means that you have less credit available to you. Cancel one card per year," says Elle Kaplan, chief executive of Lexion Capital Management in Manhattan. When closing accounts, close newer accounts first. Older accounts have longer credit histories, and 15 percent of your credit score is determined by how long you have used credit, says Bendix.

Don't commit cardinal sins: What makes this list? Says Steve Wolpow, a CPA in Melville, "Declaring bankruptcy, forcing a lender to foreclose, and forcing lenders into debt settlements."