Introducing someone to the thrill of our sport is good for your karma, and it's good for your skiing: Teaching reinforces the basics - which you've probably let slide in your complacency. Go at your students' pace, and work toward their goals, not yours. Break the lesson into manageable chunks; a good rule of thumb is to introduce new skills on old terrain. Show your student what a move or drill looks like, then let him try it. Remember, above all else it has to be fun.