Interface. Is the "look and feel" of the interface consistent? Is every screen recognizable as your product? For example, is there a common background and/or color scheme for all screens? Common screen layouts?
Function/Appearance. Do all object that appear the same, function the same? E.g., are Help, Exit, and Search objects in the same spot on all screens? Do they have the same design, color, etc.?
Text characteristics. Are the text characteristics constant from screen to screen. E.g., is Ariel 14 point bold italics always used only for chapter titles? Does blue underlined text always represent a hyperlink?
Semantic characteristics. ARe metaphors and icons used consistently throughout the interface? E.g., does a magnifying glass mean the same thing every place it is used? Does a green cat always mean Help?
Navigation. Are navigation objects and steps consistent throughout the interface? Are screens linked consistently? E.g., Previous/Next buttons, etc.
Interaction tools. Are interaction tools like mouse pointers, touch screens, joysticks, used consistently?
Conventions. Are conventions familiar to the user employed consistently?
Screen configuration(s). Are all related items on the screen grouped together visually in a format that makes sense?
Labels. Are labels on buttons, menus, and titles used consistently?