For record number use "Auto enter serial" - set it in Field Options dialog box.
Auto enter option is very good.
There are several other options but auto enter is the easiest.
To set the auto-enter options as suggested by Little Dog,
Select Manage | Database | Fields.
Find the field for which you want to set such an auto-enter option.
Double-click it and select the auto-enter tab. You'll find options to enter:
a serial number
the account name used to log in to the file
the User Name set in Edit | Preferences
You can even create your own calculation to be auto-entered.