If you paid off all of your collection accounts after being turned down for a mortgage how should you try to improve your credit?
What you need to do is obtain a copy of your credit report. These are agencies that keep track of people's debts and credit ratings etc., and whenever you apply for a loan or credit card or mortgage etc., the bank obtains these reports from these agencies. There are 3 major credit reporting agencies in the USA, and you can get a copy of your credit report from them for free, or for a minimal fee. Study it to see if there are any errors, or debts which have been paid off etc. Then you have to write to the credit reporting agency and ask them to make the specific corrections, or remove erroneous information. Then it is up to them to prove that the information is wrong, or remove it.