If you haven’t joined the refinancing boom, there’s still time to lock in today’s interest rates, which remain at historic lows. To do that, however, you need to be in the “right” geographic area and meet the strict criteria lenders are now scrupulously enforcing.

The refi surge peaked in mid-April and has been ebbing since then as rates have crept up. But refinancing still makes up more than two-thirds — 69.3 percent — of all mortgage activity, according to the Mortgage Bankers Association. Yet that doesn’t mean it’s as easy to refinance in Phoenix as it is in Philly. In markets in which property values spiked and have fallen hard, fewer homeowners have enough equity in their homes to meet today’s qualifying standards to refinance than in markets in which values never boomeranged.

Guaranteed Home Mortgage Co. in Westchester, N.Y., with offices in 31 states, is seeing both strong and lackluster refi business depending on the strength of the underlying real estate market. It's completing 50-70 percent fewer refis in what its president, David Wind, calls “declining market areas” — those in which values have plunged — than in what he calls “mature markets,” which haven’t experienced the boom and bust.

Mature areas are places like New Hampshire; York, Pa.; Saratoga, N.Y.; and pockets of Florida, such as Orlando and Dunedin,” he explains. “Declining market areas include Cleveland and Detroit, which have been decimated.

In hard-hit Arizona, Roy Meshel, vice president at W. J. Bradley Mortgage in Scottsdale, is seeing an increase in refis among homeowners who bought before the bubble burst and invested more than a minimal down payment. Even so, Meshel’s company turns down about 40 percent of callers seeking to refinance because they bought at the peak of the market with low or no down payment. For those homeowners, plummeting property values have left them without enough equity to qualify.

The story is no different for Christopher M. George, president of CMG Mortgage in San Ramon, Calif., which operates from Illinois to the West Coast. “We’re seeing heavy activity in Washington and Northern California and some activity in Colorado, Oregon and Utah,” he says. “But parts of Los Angeles are still dormant, and we don’t see a lot of activity in Las Vegas.”

How much equity do you need to qualify to refinance? If you currently have a government-backed Federal Housing Administration loan, the answer is zero. You can refinance to a better interest rate through an FHA Streamline refinance as long as you’re current on your payments.

If you have a mortgage owned by Fannie Mae or Freddie Mac, you don’t need any equity, either. You can refinance up to 105 percent of your first mortgage even if you have a second mortgage. “You could end up with a 130 percent loan-to-value ratio between the two mortgages,” says Meshel. “The second mortgagor must agree to remain subordinate to the first. Many will do that because if their borrowers are in too bad a position, they may walk away from the home, and in a foreclosure, that second mortgagor will get nothing

To learn whether one of those agencies holds your mortgage, visit Fannie Mae or Freddie Mac and enter your address.

If you don’t have a mortgage owned by Fannie, Freddie or the FHA, consider refinancing into an FHA loan because you’ll need only 97 percent equity. That means that if your home appraises for $100,000 today, the total of all of your mortgages — including home equity loans — can’t exceed $97,000. For a home appraised in today’s market at $250,000, your total mortgage debt can’t exceed $194,000.

Conventional loans — those not backed by the federal government — require more. “For a conventional loan, you’ll need 95 percent equity,” says Robert Davis, a mortgage consultant with Primary Residential Mortgage in Owings Mills, Md. “If you’re taking cash out, you’ll need at least 90 percent.”

In addition to equity requirements, lenders also impose credit score minimums to refinance. For most, a score of 620 is the floor today (if a couple are refinancing, lenders consider the lowest score between them). “Very rarely will there be a credit score exception,” says Davis. “Some lenders will go down to 600 because of the credit crunch, but most have raised their minimum because there’s a drastic increase in the default rate even for [homeowners] with a score of 610 or 600.”

Though 620 is the bottom, many lenders impose higher minimums at the insistence of their funding sources. “They say, ‘You can do whatever you want, but if you want to use our money, you have to require 680,’” explains Wind.

Another important factor lenders consider is your debt-to-income ratio. That measures the amount you owe on your mortgage, credit cards, car loans and other debt. Generally, you’ll qualify if your debt totals less than 45 percent of your income.

Don’t be discouraged if you don’t qualify in today’s challenging economy. “People seem to have forgotten that credit is like a wound and that it will ultimately heal,” says George. “The sooner you begin recovery, the sooner you’re recovered. You may have to sacrifice, but you’ll work your way back up that ladder and eventually get an opportunity to refinance.”