- Create your new custom object with the name you want but don’t give it any fields yet.
- Download the Force.com IDE (if you don’t already have it)
- Connect it to your instance of Salesforce.com
- Set the metadata settings when you connect it to download your custom objects.
Now you’ll find representations of both your source and destination custom objects in XML. You can just copy most of the fields from the source object, paste them into the destination object, save, and voila — all the fields will be there. You can add other fields this way manually if you want too, but I find it’s sometimes easier to add fields using the web UI.