One of my favorite topics of conversation is using geospatial data in Civil 3D. Civil 3D is built on Map 3D, so you get the advantage of several methods of importing shapefiles, arcinfo data, raster imagery, and much more. I'll be showing some techniques in Civil 3D 2010, but this capability has been around for a few releases and much of it should work similarly in Civil 3D 2009, 2008 and 2007. I originally wrote a process for Civil 3D 2007, which you can find here at "Can you do that in CAD? Yes!"
You can connect to data through the FDO a few different ways, but a really easy way is to just drag your shapefile into the drawing area. This animated image shows you how- click on the image to see the animation.
Next, bring in the Map Workspace. I typically get it by typing "mapwspace" in the command line. Then right click on the data you'd like to study. Choose Edit Style.
In the dialog, use the pull-down to choose which property of the data you'd like to theme. For example, this data has a field that breaks the soils up into categories of "well drained", "poorly drained", etc. I want to look for well drained soils, so I will chose that field. The theme will make each different drainage type a different color. You can play around with the colors using that style range option.
Then I can press the Label Ramp button and it brings up a dialog which will automatically make a label for each polygon. You can label the same data as your color theme, but you can choose anything else. For example, I could color the polygons by drainage properties, but label them with their soil name of hydrologic group.
Once I press OK to dismiss both dialogs, I can see a nice color map.
Let's say I wanted to isolate just the well drained soils. I can make a query to sort things out.
For this example, I made a property query and used the "get values" button to provide a list of properties so that I didn't have to remember how to spell "Well Drained" (or remember what my choices are).
Once I press OK, my map is redone, and those well drained areas are isolated.
A few weeks ago, Lucy did a webcast about using geospatial data that covers a lot of techniques like this to help you study sites during the concept phase, bring in data to get started, create maps and exhibits, and other tasks using Civil 3D 2010. You can watch other archived webcasts here.