Your Mortgage : Check Your Credit Before Mortgage Shopping : Home Loans: Before attending open houses, make sure that credit bureaus give you a clean bill of health. This will make it easier to get loan.

Tuesday marks the official start of spring--and also the start of the unofficial prime home-buying season.

More homes are sold in the spring than at any other time of the year, in part because the weather is usually good for home shopping.

In addition, families who buy a house in the spring can close escrow by summer, meaning that their kids don’t have to change schools in the middle of a term.

If you’re planning on joining the open-house crowds over the next few months, you can get a head start on all those other buyers by giving your credit history a checkup and making a few other moves before you buy a house and apply for a mortgage loan.

Start by ordering a credit report on yourself from TRW or some other company. They’re found in the Yellow Pages of the phone book under the heading of “Credit Reporting Agencies,” and they usually charge between $8 and $15 for their services.

If your credit report has any blemishes that you feel are unwarranted--for example, a creditor who says you missed a payment, even though you’re sure you made it--contact the creditor immediately and try to clear up the problem. Receipts and canceled checks can prove that you made your payments on time.

Assuming you resolve the matter in your favor, both you and the creditor should send a letter to the various credit-reporting agencies explaining that the dispute has been satisfactorily resolved. Follow up by contacting those agencies to make sure they’ve corrected and updated your credit file.

Even if you can’t resolve the problem, send a letter to the reporting agencies to explain your side of the story. This will show your lender that the matter is being disputed, and that you’re making efforts to clear up the issue.

Once you’ve checked up on your credit and started smoothing out any problems, it’s time to get pre-qualified by a realtor or lender. This will help you determine how big a loan you can get, based on your earnings, down payment and debt obligations.

“Pre-qualifying saves you time in the long run because you won’t waste time looking at homes that you can’t afford,” said Wilma Buckel, underwriting manager of Western Bank Mortgage Co. in Costa Mesa.

Getting pre-qualified usually costs nothing, and it also helps you to get your financial house in order--an important first step in the home-loan process.

There’s one other benefit to pre-qualifying: It makes you a more credible buyer when you make an offer on a house.

“If a seller knows that you’re pre-qualified, he’ll have a higher confidence level in your offer because he knows that you’ll be able to get the loan and close the deal,” said Paul Yoder, district manager in the San Clemente real estate brokerage office of Grubb & Ellis.

If you have had credit problems in the past--or even if your credit report erroneously shows some payment problems--don’t be afraid to tell your lender about them.

“We can understand if you had some financial difficulties one time because you were laid off and had some trouble finding another job, or if you had medical problems and had trouble meeting your bills,” banker Buckel said.

“The important thing is to be honest and open with us and to have a good explanation for what happened. We don’t like surprises.”

Letters of references from previous employers can establish that you were a good worker; copies of letters you sent to potential new employers can show that you didn’t dawdle when looking for a new job.

Copies of doctors’ bills can document long illnesses, which can help explain why you missed payments to creditors.

If you’re thinking of changing jobs while you’re house hunting, you might want to think twice. “If you’re staying in the same line of work but will be earning more money, then that’s fine,” said Palma Jarvis, a vice president with HomeFed Bank in San Diego.

“But the lender will be skeptical of someone who has changed jobs every six months, especially if the changes weren’t really promotions, or if they involved a career switch. We like to see a history of steady employment in the same line of work.”

If you’re planning to sell stocks or other assets to raise a down payment--or if you’ll be getting financial help from your parents or another relative--it’s a good idea to get the money in the bank now.

That’s because most lenders don’t just ask for the current balance of your bank accounts when they verify your deposits: They also ask for the average balance for the past three or six months.

“If you get that money in the bank now, your average balance will be higher when we go to check it,” Jarvis said. “That makes you a little stronger applicant.”

When lenders look at your loan application, they’ll pay particularly close attention to your “debt ratios.”

If you plan to make a 20% down payment and want a fixed-rate loan, the lender will probably let you to devote up to 28% of your gross pre-tax monthly earnings toward your housing expenses--including the mortgage payment, property taxes, insurance, utility bills and any association dues.

However, your combined housing expenses and all other debt won’t be allowed to exceed 36%.

If you’re going to put only 10% down, the lender probably won’t let your housing expenses exceed 25% of your gross income. Housing expenses plus all your other debt won’t be allowed to gobble up more than 33% of your pre-tax paycheck.

If you’re planning to pay off some of your debt to lower your ratios, it’s usually best to pay off so-called “installment” loans--auto loans, student loans and the like--instead of “revolving” loans, such as credit card bills.

That’s because lenders typically don’t pay much attention to revolving accounts that will likely be paid off within 10 months, but they do factor in installment debt, even if the loan will be paid off soon.

Although lenders use debt ratios to help gauge your borrowing power, they’re really only guidelines. A lender may accept slightly higher ratios if you have a spotless credit record, or insist on even lower ratios if you have had credit problems in the past.

They also are usually willing to accept higher ratios if you’re asking for an adjustable-rate mortgage instead of a fixed-rate loan, in part because they’ll be able to raise the interest rate on your loan as time goes by.

Lenders will also accept higher ratios if you make an unusually large down payment. “If you make a 25% down payment, some of our loans will allow you to use as much as 45% of your gross monthly income to make your housing payments,” said Jarvis at HomeFed.

One other tip: Avoid making any big-ticket purchases until your loan has been funded and you’ve settled into your new house.

“When you’re applying for a mortgage, you want to show the lender as much savings as possible and as few debts as possible,” Jarvis said. “If you want a new car, a boat or even furniture, wait until you close escrow before you go shopping.”