In pretty much all applications that have a menu bar, some of the items have an ellipsis (...) after them, and some don't. Is there a well known convention on when to put that ellipsis there and when not to? When do you do it? Do you do it?
I have looked at various windows applications, and this is what I have come to:
Ellipsis
No ellipsis
But then there always seems to be menu items that doesn't follow this rule. For example the Help items (How do I, Search, Index) and the Find and Replace (Quick Find, Find in Files, Find Symbol) in Visual Studio.
So after thinking about it a bit more I now think this might be the thing:
Ellipsis
No Ellipsis
What do you guys think?
The crucial factor is whether the menu option requires additional information (input or a selection) before it carries out the operation. So Help-About doesn't require an ellipsis, but File-Open does. That's what the Microsoft, Apple and KDE guidelines say anyway.
Microsoft Windows applications are supposed to follow Microsoft's "User Experience Guidelines". Here's what they say about ellipses on menu items.
While menu commands are used for immediate actions, more information might be needed to perform the action. Indicate a command that needs additional information (including a confirmation) by adding an ellipsis at the end of the label.
This doesn't mean you should use an ellipsis whenever an action displays another window—only when additional information is required to perform the action. For example, the commands About, Advanced, Help, Options, Properties, and Settings must display another window when clicked, but don't require additional information from the user. Therefore they don't need ellipses.
David's answer cites the KDE 3 user interface guidelines,
Notice that every item in a menu that first opens a dialog requiring additional information must be labelled with a trailing ellipsis (...) (e.g. Save As..., Open...). There's no space between the menu item and the "...". A simple confirmation dialog is not considered a dialog that requires additional information.
The Apple Human Interface Guidelines say:
When it appears in the name of a button or a menu item, an ellipsis character (…) indicates to the user that additional information is required before the associated operation can be performed. Specifically, it prepares the user to expect the appearance of a window or dialog in which to make selections or enter information before the command executes. Because users expect instant action from buttons and menu items (as described in “Buttons” and “Menu Behavior”), it's especially important to prepare them for this alternate behavior by appropriately displaying the ellipsis character. The following guidelines and examples will help you decide when to use an ellipsis in menu item and button names.