one ampersand is all that is needed. if you have a lot of variables you might consider placing them in hidden fields in a form as there is a limit to how much can be passed through the URL (granted it is about 2000 characters, but still....)
As for you question about multiple lines, just keep on typing...just put all the details in the anchor tag <a href=...> and keep the actual link text short...
hth
Bastien