Add a short instruction.

Author: fukamachi

README.md

@@ -16,6 +16,10 @@ See [benchmark.md](benchmark.md) for the detail.
 
 ## Usage
 
+Use `clack:clackup` or `woo:run` to start a web server. The first argument is a Lack "app". See [Lack's README](https://github.com/fukamachi/lack#readme) for instruction on how to build it.
+
+Remember to pass ":debug nil" to turn off the debugger mode on the remote environment. Otherwise, your server will go down on any internal errors.
+
 ### Start a server
 
 ```common-lisp