Are you using folders?
You may want to change any Generic Reference type to a more specific type, e.g., Journal Article Reference; Conference Proceedings Reference; Book, Whole Reference. To change:
Edit | Reference Type [make a selection]
Best practice: Select a few of your more complicated references, e.g., video format, customized fields, personal notes and use them as a sample export. You will immediately see which fields transfer seamlessly into Zotero and which ones will require editing.
File method: Select Save As. Some browsers will automatically save as a .txt file, others use a different extension. Change the filename to the folder name, and, if necessary, change the extension to .txt.
Copy method: Select All | Copy
File method: Select File | Import | [browse to file] | Open. Zotero will create a new collection/subcollection with the filename you used when you did the Save As.
Copy method: Create a collection and name it. You will probably use the same name as your RefWorks folder.
Open that collection and Select File | Import from Clipboard - Zotero will deposit the references in the open collection.
Fields with no equivalent in Zotero, e.g., Personal Notes, Author Address/Affiliation, Database, will appear in a note titled "the following have no corresponding Zotero field." Items with notes/attachments have a right-pointing arrowhead on the left side of the title. Click on the arrowhead to reveal the note/attachment names; click to open.
Anything in the RefWorks Personal Notes field will transfer as unformatted text into a Note in Zotero titled 'The following values have no corresponding Zotero field.' The text will be preceded by the value PA.
To retain the formatting of your Personal Note, e.g., paragraphs, bold, italics
NOTE: If you copy the note directly off the RefWorks screen and paste it into a Zotero note, the formatting will be kept, but a large amount of extraneous HTML is included