In the old days, we used category ids to import products into multiple categories.
In Magento 1.9, we now use Category Paths "parent-category/child-category"
How do I import a product into two categories at one time?
To increase the difficulty, my category names have spaces in them.
Said another way, is there a delimiter to use between category paths?
I've tried comma, semi-colon and pipe.
I have described that in detail in my blog post at http://www.integer-net.com/2012/04/04/importing-products-with-the-import-export-interface/ in the section "Categories". In short, you have to have seperate lines for each category. All lines except the first line for each product should not have the base values like SKU, websites and so on.
Spaces are no problems, you don't even have to escape them. In my example (old demo data) it is just "Electronics/Cameras/Digital Cameras".
I have 1.9.2 and still use catagory id's seperated by a comma.
You can't do that if you are using the "ImportExport" import module which is the default import method since Magento 1.5.
You can still use the old "Dataflow" module (I think you are using that), but it's a lot slower (magnitudes; see my comparison of the import methods at http://www.integer-net.com/2014/05/27/product-import-with-magento/).