Tweetsmash is a freemium Twitter curation tool. You can use the basic features for free, but you have to pay for advanced features. You can sync your Twitter bookmarks with Zotero, and the articles you bookmark on Twitter are automatically added to your Zotero library.
: this button allows you to manually create new references if you cannot find the reference online.
Save the PDFs you want to add to your library on your computer, then drag and drop them into your Zotero library. Zotero will automatically attempt to retrieve metadata (title, author, journal...) from the PDF. The PDF will also be renamed according to the parent metadata.
Zotero uses "translators" to convert the data from library catalogues, databases, or other websites such as Google or Amazon. When you viewi a website, if a translator is available, a small icon appears in the URL bar. Just click on it, and the reference will be downloaded.
There are different icons, for each type of document: blue for books 
, white for journal articles 
,etc. If there are multiple references on a web page, the folder icon 
will appear and you can click on it to select the references you want to download.
There are Zotero translators for:
: this button allows you to add references using the ISBN (International Standard Book Number) or the DOI (Digital Object Identifier). All books published recently have an ISBN. The DOI is an identifier for electronic documents such as web pages, or articles published in electronic journals, but most web pages do not have DOIs. However, you can find DOIs in some bibliographic databases.
You can use RSS or ATOM feeds to add the references documents of interest directly to a Zotero library.
Click on the 
button, select "New Feed" and enter the URL or the OPML. The reference can then be added directly to a Zotero library, by clicking the "Add to My Library" button or by first selecting a specific collection.
