Zotero
Adding Items from the Web
When you visit a page that Zotero recognizes as a bibliographic item, such as an item in a library database, an icon will appear in your browser's toolbar. The appearance of the icon depends on the type of resource being viewed, with the most common being the book icon and the lined page icon representing a journal article. Some of these are very difficult to see.
If you're on a web page that Zotero can't identify as a particular type, you'll see a generic page icon. Clicking on this will add a basic entry (often just the URL and the date accessed) for the page to your Zotero library, along with a snapshot of the page.
Adding Items as Files
If you've downloaded a PDF of an article that you'd like to include in your Zotero library, you can just drag the file in. Zotero will usually be able to scan the file and find the citation info. This can save you a lot of time if you've already downloaded a lot of sources--just grab all the files and drag them in!
Adding Items with no Electronic Record
If you need to add an item for which you have no online record, you can add the item manually using the "new item" button and choosing the type of resource that you want to add.
Check Your Data!
When you save an item to Zotero, look at the data that is being saved. Zotero may have missed something that you need (like the abstract) or recorded data incorrectly (e.g., forenames and surnames mixed up, title in all caps). It's easier to fix mistakes like this when you're collecting the data that it is to go back later when you're trying to put together your bibliography.
One very common problem is for the data from an item to come in with some fields in ALL CAPS. As of Zotero version 7, you can correct this by clicking on the ellipsis to the right of the field in the item details panel and selecting "Title Case" or "Sentence case."