With the update of Google Drive available to people and will more than likely be pushed to everyone soon, there is a new sharing window that pops up. You have pretty much the same options as before but you just need to click in different spots. The official Google Drive post can be found at http://googledrive.blogspot.com/2014/09/sharingupdates.html.
Just like before, you can click the Share button while in a file or by clicking the icon to bring up the sharing window.
The sharing window now looks like this.
To get a link to share out the file so that anyone with the link can view (which is the default setting), click on the “Get shareable link”. It will turn green when it is turned on. You can change the settings after you click it initially so that you can also allow others to comment or edit with just the link.
The link to the file will automatically be copied into the clipboard so that you can paste it into anything you want. Just click on the down arrow to the left of the “Copy link” button to change the sharing options with the link.
You can add specific people to be able to edit, view or comment just like before by typing their account name into the People box. You can change the settings to the right of the names to give them their specific type of access.
You can still send an email to people when you share files with them. When you add their name to the sharing box, a new box will pop up below it which will contain the note that you send to people. You can keep from sending an email by clicking the box that says “Notify people via email”.
You can get back to the old sharing window by simply clicking the Advanced button in the bottom right.