Always provide visual feedback for explicit selections as the user makes the selection, so that the user can tell the effect of the selection operation. Display the appropriate selection appearance for each object included in the selection set. The form of selection appearance depends on the object and its context.
Note 
For more information about how to visually render the selection appearance of an object, see Chapter 13, "Visual Design." For more information about how the context of an object can affect its selection appearance, see Chapter 11, "Working with OLE Embedded and OLE Linked Objects."
You may not need to provide immediate selection feedback for implicit selection; you can often indicate the effects of implicit selection in other ways. For example, when the user drags a scroll box, the scroll box moves with the pointer. Similarly, if the effect of selecting a word in a paragraph implicitly selects the paragraph, you would not use selection appearance on the entire paragraph, but rather reflect the implicit selection by including the paragraph's properties when the user chooses the Properties command.