Lenders will generally pull your credit at least twice -- when you originally apply and shortly before closing (as happened in my situation). If there are any significant differences between the two, such as a new account or a significantly higher debt balance, it could lead to delays and could even disqualify you for the mortgage. Be safe -- just leave your credit alone until you've signed your closing documents.
"I don't know what I would have done without the help of Iowa Mortgage Help. After a long and expensive battle with medical bills, I faced foreclosure of a home that has been in my family for over 100 years. I was finally able to get a successful loan modification and a payment I can afford in order to take care of my home. I'd have lost everything if it wasn't for their assistance."
When you apply for a mortgage, you'll need to document your income, employment situation, identity, and more, so it can be a good idea to start gathering the necessary documentation before you walk into a lender's office. This isn't an exhaustive list, but you should locate your last couple of tax returns, bank and brokerage statements, pay stubs, W-2s, driver's license, Social Security card, marriage license (if applicable), and contact numbers for your employer's HR department. Here's a more comprehensive list that can help you determine what you'll need.