In general, the documentation you will need includes:
Check or credit card for your credit report fee
Property Information (if you already have a contract on a house)
Fully ratified Purchase Agreement.
Copy of legal description and MRIS sheet (as available).
If you are selling your current home, copy of listing contract.
If you have sold your current home, copy of settlement statement (HUD-1).
Income & Assets
Pay stubs for the last 30 days with YTD info.
For the past two years:
Statements for each bank (checking/savings), mutual fund, investment and/or retirement (401k, IRA, SEPs, etc) account for the last two months.
Estimated value of personal property and furniture.
If you have made any large deposits to your accounts:
If you own more than 25% of a business:
If self-employed:
If you own rental property:
If you are retired:
If you receive Social Security:
If you are counting child support as income:
Debts
Names, addresses, account numbers, balances and monthly payments on all current loans.
Explanation of credit report anomalies, including:
VA Loans
Copy of DD Form 214, Report of Separation.
Miscellaneous
Photo ID and proof of Social Security number.
Residence addresses for the past two years.
If applicable, a copy of your divorce decree or separation agreement.
If you are not a citizen, a copy of the front and back of your alien registration ("green") card. 
