When your stuck entering a lot decimal places, have Excel make your life a little easier by entering them for you automatically.
To set a fixed number of decimal places, go to Excel Options, Advanced tab, check Automatically Insert a Decimal Point, and set the Places box to the proper number of decimal places, then click OK. (In Excel 2003 and in Excel 2008 for Mac go to the Edit tab to find this option)
The current data in the worksheet will not be affected.
Once this option is turned on entering 4836 becomes 0.4836 and entering 10345 becomes 1.0345. A neat way to avoid entering the decimal point.
When your done, just turn off the option and everything goes back to normal. Sweet!