If you have everything with you when you visit your lender, you'll save a good deal of time.
You should have:
1) Social security numbers for both your and your spouse, if both of you are applying for the loan.
2) Copies of checking and savings account statements for the past 2 months.
3) Evidence of any other assets like bonds or stocks.
4) A recent paycheck stub detailing your earnings.
5) A list of all credit card accounts and the approximate monthly amounts owed on each.
6) Copies of your last 2 years' income tax statements.