Cartographic Symbols & Map Symbols
Ungroup a symbol to select and modify its component artwork.
If the symbol is an Illustrator symbol instance that you've dragged onto the artboard from the Symbols palette, use Object > Expand to convert it to artwork so that you can ungroup and edit it. When scaling the symbol artwork, be aware of the Scale tool's Scale Strokes & Effects checkbox. Keeping it checked will modify the stroke width of the symbol's linework. Unchecking the box will keep the stroke width of the linework unchanged.
When you edit a line or area Style, you can drag the preview icon in the upper-left of the Appearance palette and drop it in the Styles palette to create a new Style. If you hold down the Option (Mac) or Alt (Windows) key, you can drop the icon on an existing Style to change it (and all artwork painted with that Style).
You can add Illustrator Effects (like drop shadows) to any symbol by selecting it and choosing the effect from the Effects menu. To change the effect later, select the symbol and in the Appearance menu, double-click the name of the effect. An effect dialog will pop up, allowing you to modify effect parameters.
The Area Symbols use transparency (in the Appearance palette you'll see that the Mezzotint component has a transparency value and a blending mode). Be sure to choose Effect > Document Raster Effects Settings and set the resolution and other parameters to match the output you plan. Set resolution high for printing or keep it low for screen display and exporting web graphics.
If you are printing the map, be sure to choose File > Document Settings > Transparency, too. In this dialog, set the Flattening Settings to a position recommended by your printer. Transparency is a known culprit in printing problems--let your printer recommend how artwork with transparency should be flattened or otherwise handled. As an alternative, you can rasterize the area symbol artwork by bringing it into Photoshop, saving the file as a TIFF, and then bringing the TIFF file back into Illustrator.
Check here to view a detailed description of all the symbols in the collection.