This one is straight out of the help file, but handy nonetheless:
Updating a 2008 Render Appearance
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- In Revit Architecture 2009, open a project.
- Click Settings menuMaterials.
- In the left pane of the Materials dialog, under Materials, enter not upgraded in the search field.
- Select a material from the list.
- On the Render Appearance tab, click Replace.
- In the Render Appearance Library, select the desired render appearance for the material, and click OK.
- If desired, modify properties for the render appearance.
- Click Apply.
- Repeat Steps 4 through 8 for other materials whose render appearances were not upgraded.
- In the Materials dialog, click OK.
- Save changes to the project.