OS X Mavericks adds a bunch of smily faces that automatically replace the text-based versions you type, but you can call them up anytime you like. Just press Command+Control+Space to get an extensive panel of emoticons/emoji and special characters you can insert into any text box.
Now see the button at the top-right of the palette? A single click converts the palette into the more classic form of the Characters window you might be familiar with from OS X Mountain Lion and earlier.
Use the search field to find exactly the kind of pictograph you're looking for. Keep your search phrase as general as possible. A search for "triangle," for example, returns a lot more possibilities than "left triangle."
Once you've found the item you wish to insert, just drag it from the center pane within the Characters window to whatever text you're editing.
You can click the Add to Favorites button for any pictograph to add often-used symbols to the main display of your Characters palette. Once added, these items appear beneath the most recently used items list.
To add or remove items from your favorites list, you need to be using the old-style Characters window, which you access from that top-right button. Use the Add to Favorites and Remove from Favorites buttons when you view individual items. After defining at least one favorite, a complete list of favorites appears at the top-left of the Characters window, just below the Recently Used list.