I'm going to nitpick on your terminology, 'cause it's important. Arc is a dialect of Lisp. There are many Lisps (Common Lisp, Emacs Lisp, AutoLISP, Clojure, etc.), but I'm going to go with you meaning Common Lisp.
Have you checked out the tutorial? (http://ycombinator.com/arc/tut.txt) It's a good introduction, and you can diff what you see with what you would write in Common Lisp in your head pretty easily, as the code examples are small.