Command-line interface user input question.

How would I go about efficiently polling for user input on a command line interface using the serial port on the Arduino?

You might want to provide more details about what you are trying to do. What is the Arduino going to be doing? What is it connected to? What is sending it serial data?

How would I go about efficiently

Define "efficiently".

Have a look at "Serial.available ()". http://arduino.cc/en/Serial/Available