To rename multiple files, select all the files you wish to rename (in a previous post I looked at various ways of selecting multiple files). Then either right-click on any of the files and select Rename from the context menu (this method is demonstrated in the following video), or press F2. Type in the new name of the file - including the file extension if it is visible (eg. .doc, .jpg, etc) - and press Enter. All the other selected files will be renamed with an individual number in brackets. So, if you type in photo.jpg, the next file will be called photo (1).jpg, the next photo (2).jpg and so on.
If you think this is a little messy, you can type in the (1) yourself. For example, if you rename the selected file to photo (1).jpg, the next file will be called photo (2).jpg etc.