While most other Lisp Swank Server implementations are started from within Emacs, there is no single Clojure Swank Server you can start.
Each Project uses a different Classpath and other customizations like JVM Options.
Although its possible to start a Leiningen based Swank Server using elein, I prefer start the Swank Server using the shell.
autoconnect is implemented using "emacsclient" from within a Leiningen hook. So you must have Emacs running in Server Mode.
In your emacs config:
Add the lein-swank-autoconnect hook/dependency to your Leiningen project:
(defproject foo "1.0.0-SNAPSHOT" :description "FIXME: write" :hooks [leiningen.hooks.swank-autoconnect] :dependencies [[org.clojure/clojure "1.2.0"] [org.clojure/clojure-contrib "1.2.0"]] :dev-dependencies [[lein-swank-autoconnect "1.0.0"] [swank-clojure "1.2.1"]])