Almost one third of Americans have low credit scores, which are bad at the best of times but can cause serious problems in the long term.

Isolate Your Score Killers

To solve a problem, you must isolate its causes. Credit scores follow a poor-to-excellent scale based off credit dealings reported to the three major credit bureaus: TransUnion, Experian and Equifax. There are five factors which companies use to rate your credit score: the age of your credit accounts, your payment history, your credit utilization, your mix of credit accounts and your history of applying for credit. Some are far more heavily weighted than others. Your payment history is the most important factor, with late payments counted as the greatest offense.

Credit utilization comes in at second, covering the amount of revolving credit (such as credit cards) you’re currently using compared with the limits set on those accounts. This is done to see if you’re spending beyond your means while in debt. The age of your credit accounts and the mix of your credit accounts are less important. The former looks at the age of your oldest account and the average age of all your accounts. The latter looks at how you handle your different types of credit, installment accounts (e.g. mortgages) and revolving accounts (e.g. credit cards). Creditors want you to see you handle both types of account responsibly.

Installment accounts will generally improve your rating whereas indebted revolving accounts will damage it. Your history of applying for credit is the least important factor, if you applied for too many recently your rating can take a hit, but this effect usually wears off in a year.

Where to Start

The first thing you’ll need in order to start repairing your credit is your credit reports which list your history and score. You can get free copies of these reports once per year under the Fair Credit Reporting Act. Get your reports from each of the credit reporting agencies since they’ll contain different data impacting your score in different ways. You won’t know which is being used by a lender so you need to know that all of them are accurate.

You should find what is causing your bad credit, whether it is unpaid collections, bankruptcies, late payments or a combination of several factors. You won’t be able to fix all of your bad credit in a month; some problems take longer than others. Credit utilization is best kept below 30%, and can be reduced by paying off balances.

Bankruptcies can take 10 years from the filing date to be removed, late payments, collection accounts, foreclosures, short sales, repossessions, judgments, tax liens and charge-offs take 7 years.

Fixing Inaccuracies

You can expect to fix inaccurate information on your credit reports far faster as credit reporting agencies are required by law to respond to disputes within 30-45 days and if they find in your favor they’re required to remove the mistake immediately. Multiple errors require separate dispute letters and each and should be filed as soon as possible.  Check for inconsistencies: outdated information, incorrect balance information, unfamiliar collection accounts. Identity theft, as well as error, can cause inconsistencies. Be wary that you’ve correctly identified an error because if you take it to court and the judge orders you to pay the debt that decision will be included on your credit report. Make yourself aware of how long does a judgment stay on your credit report, which can be up to 10 years. You may file a motion in court to dismiss or vacate the order if you believe the judge’s decision is mistaken, but you need sufficient documentation to contradict it and it’s a risky route.

Each major credit reporting agencies have different dispute processes. In order to get positive credit history, you should pay down your credit card balances, pay outstanding collection accounts and refrain from closing old accounts until you’ve sorted them out as this can affect your credit utilization.

Credit Repair Companies and Software

You can use a credit repair company or credit repair software but beware. A credit repair company may be more efficient at detecting problems with your credit history but it doesn’t have any special powers you don’t have or knowledge you can’t obtain. Credit repair software, on the other hand, is downloaded and self-operated, analyzing your credit reports to look for errors, automatically producing a dispute letter if it detects any, which you can then forward on to the credit bureau in question.

The best means to build your credit is to pay your bills on time and dispute errors on your credit reports. If you lack the time or energy, consider a repair company or software.

Lucas Allan writes about a variety of personal finance topics. A parent of college-aged kids and younger, his articles appear on a range of money and parenting blogs.