The Theme should be widgetized as fully as possible. Any area in the layout that works like a widget (tag cloud, blogroll, list of categories) or could accept widgets (sidebar) should allow widgets.
Content that appears in widgetized areas by default (hard-coded into the sidebar, for example) should disappear when widgets are enabled from Appearance > Widgets.
Display archive title (tag, category, date-based, or author archives).
Display a list of posts in excerpt or full-length form. Choose one or the other as appropriate.
Include wp_link_pages() to support navigation links within posts.