The length of the text-entry portion of an edit box should roughly equal the length of an average entry. When in doubt, use a character width of 10 for real number fields and 20 for text fields.
The label of an edit box should end with a colon (:).
If there are restrictions on what users can enter in the edit box, put a text tile to the right of the edit box that briefly explains these restrictions. If users need to enter a file name, for example, there's no need to explain what a file name is. But if the string is a number that cannot exceed 100, a reminder of this limit is a good idea.
For data, such as points, provide two or three edit boxes rather than require users to remember the Command line syntax of point entry. One exception is an edit box intended specifically for entering advanced syntax, such as the wild-card pattern edit box in the AutoCAD File Search dialog box.