You can import AutoCAD files into Autodesk Revit and then manipulate it from there as a Revit file or you can xref the file. See this tutorial on how to xref CAD files.

NB: Importing a CAD file will not automatically convert the drawing to 3D.

To import as a link file:

1. Go to the insert tab.
2. Select “link CAD“.
3. Browse for the CAD file that you wish to link.
4. On the positioning tab leave the default position ”Center to Center”. You can also change that to “Origin to Origin”.
5. On the “Place at” tab select the level you want to import the file. For example, level 1or level 2 if you have many levels or floors in your project.
6. Pick your color preference on the “Colors” tab. You can set the link file to show black and white, invert color or the original color.
7. On the Layers tab leave “All” selected, if you want to import all the layers from the file.
8. Leave the “Import units” as Auto-Detect.
9. Select “Open”.

Now that the file is showing in the drawing as a cross reference file. You can also turn on and off layers from Revit as you wish, the same as in AutoCAD.

To import as part of Revit:

1. Go to the insert tab.
2. Select “Import CAD”.
3. Browse for the cad file that you wish to import.
4. On the positioning tab leave the default position ”Center to Center”.
5. On the “Place at” tab select the level you want to import.
6. Pick your color preference on the “Colors” tab.
7. On the Layers tab leave “All” selected, if you want to import all the layers from the file. Otherwise, you can select which layer to import individually. By doing so it will not import any object on unselected layers.
8. Leave the “Import units” as Auto-Detect.
9. Select “Open”.

Once the file is imported you can edit the CAD drawing as a Revit file.

NB: We used Revit MEP 2010 for this tutorial. I believe the steps are similar in Revit MEP 2009. You start from File, Import/Link, CAD formats.

Below are two standard scale tables for Engineering and Architectural drawings.

To obtain the scale factor of an Engineering drawing scale:

1. Multiply the feet of the desired scale by 12.
2. For example 1″=50′ scale would be 50×12 = Scale Factor 600.

To obtain the scale factor of an Architectural drawing scale:

1. Multiply the denominator of the desired scale by 12.
2. for example 1/4 scale would be 4×12 = Scale Factor 48.

Working with tables in Microsoft Excel is much easier and convenient than the CAD table features in AutoCAD, and there are many ways to use your table or schedules created in Excel to be imported into AutoCAD:
• As a Microsoft Excel worksheet:
The table will look exactly like the Excel spreadsheet you created and changes can be made in Excel by double clicking on the table. In other words, it is an Excel spreadsheet hosted in AutoCAD.
Procedure:
1. Select all the cells that you want to import from Microsoft Excel.
2. Right click, select Copy or simply use Ctrl+C.
3. Open AutoCAD.
4. From the top menu, select “Edit” then “Paste Special” then “Paste” then “Microsoft Office Excel Worksheet”.

• As an AutoCAD Entity:
The Excel table will be converted to an AutoCAD table.
Procedure:
1. Select all the cells that you want to import from Microsoft Excel.
2. Right click, select Copy or simply use Ctrl+C.
3. Open AutoCAD.
From the top menu, select “Edit” then “Paste Special” then “Paste” then “AutoCAD Entities”.

• As an image or picture:
The Excel table will be converted into an image entity.
Procedure:
1. Select all the cells that you want to import from Microsoft Excel.
2. Right click, select Copy or simply use Ctrl+C.
3. Open AutoCAD.
From the top menu, select “Edit” then “Paste Special” then “Paste” then either “Picture (Metafile)” or “Bitmap” or “Image Entity”.

• As a linked Excel table:
The table will be linked to the Excel sheet so that when you make changes in Excel the table will be automatically updated in AutoCAD. This is very useful if many people share one document and constantly need updating.
Procedure:
1. Select all the cells that you want to import from Microsoft Excel.
2. Right click, select Copy or simply use Ctrl+C.
3. Open AutoCAD.
4. From the top menu, select “Edit” then “Paste Special” then “Paste Link” then “Microsoft Office Excel Worksheet”.

• As a linked AutoCAD Entity:
The Excel table will be converted to an AutoCAD table and linked to the Excel sheet, so changes made in Excel can be updated automatically in AutoCAD.
Procedure:
4. Select all the cells that you want to import from Microsoft Excel.
5. Right click, select Copy or simply use Ctrl+C.
6. Open AutoCAD.
5. From the top menu, select “Edit” then “Paste Special” then “Paste Link” then “AutoCAD Entities”.

Follow these steps to add an automatically loading LISP routine to your ACAD STARTUP.

1. Save the LISP file with lsp extension to your C drive in this directory C:\Documents and  Settings\username\Application Data\Autodesk\..your AutoCAD version here..XX\RXX.0\enu\lisp routines folder.
2. Open AutoCad and type “APPLOAD” in the Command line.
3. When the dialogue box pops up, click on
the “contents…” button in the bottom right hand corner (“Startup suite”).
4. In the Startup Suite dialogue box, select the “Add…” button.
5. Browse for your LISP file with .lsp extension that you have saved before.
6. Click Add once you find your lisp file.
7. Close all dialogue boxes and you are done.

The next time you open AutoCAD the lisp routine will automatically load without any command invoke.

In AutoCAD we often get an error message about proxy AEC objects when we open a drawing.

Proxy objects are objects that were created by an unavailable ObjectARX application such as Revit software. These proxies carry information that is not supported in AutoCAD. However, you do not need the original application to display the object in AutoCAD. You can get rid of the proxy objects by creating a new version of the drawing with all the AEC exploded.

To do that:

1. Type AECTOACAD or –EXPORTTOAUTOCAD in the command line.
2. Hit Enter for filename.
3. Type the new name for the new file.

When you open the new file you have just created, the annoying proxy error pop up will not show anymore.

A lot of times people encounter the situation where they have so many layers in a drawing and some are duplicated with slightly different layer names; for example: M-WALL-N, M-WALL-NEW or M-HVAC-EQPM, M-EQPM-HVAC. Sometimes the layer is occupied by an inserted block that is not used on the plan. Other times, the layer is not occupied by an object. If you try to purge the drawing the layer still will be there.
In AutoCAD, you can merge unused layers into another used layer by using the LAYMRG command. It is helpful in cleaning up your layers and organizing them, especially when you need to convert your drawing standard to a different given standard. That might happen if you are working with someone else or another firm who has a different layer naming convention.
To merge layers:
1. Type LAYMRG in the command prompt.
2. Select the layer you need to merge.
3. Hit enter or the spacebar on your keyboard.
4. Select the target layer you want to merge to.
5. Select or type “yes” when asked.
6. Press enter or the space bar on your keyboard.
The old layer should now be deleted and purged out of the drawings. You can merge more than one (1) layer at a time to a target layer. Simply select the layers to be merged one after the other before you hit enter or the space bar.
NB: To use this command, your merging layer should not be set as current.