The most obvious task in localizing an application is translating the strings that appear in the user interface. To create an application that can be translated without altering code everywhere, the strings in the user interface should be isolated into a single module. Delphi automatically creates a .dfm file that contains the resources for your menus, dialogs, and bitmaps. 

In addition to these obvious user interface elements, you will need to isolate any strings, such as error messages, that you present to the user. String resources are not included in the form file. You can isolate them by declaring constants for them using the resourcestring keyword. For more information about resource string constants, see the Delphi Language Guide. It is best to include all resource strings in a single, separate unit. 

For information on using resource DLLs in your applications see Creating Resource DLLs and Using Resource DLLs.