UNIX Notices (UN) was developed to study the problems in providing advice to users of complex systems. The issues studied were: what, when, and how to present the advice. The first experiment with 24 subjects examined how different presentation styles affect the effectiveness of UN's advice. The three presentation styles studied were: notice appears in separate window; notice appears only on request; notice appears in use r's window immediately. The results showed that the third style was significantly more effective than the first style. Furthermore, the results indicated that the most effective presentation method is also the most disruptive. The second experiment with 29 subjects studied how delay in the advice feedback affects the performance of UN. The treatments were: immediate feedback, feedback at end of session, and no feedback. Over a period of 6 weeks, the commands entered by the s ubjects were logged and studied. The results showed that immediate feedback caused subjects to repeat significantly fewer inefficient command sequences. However, immediate feedback and feedback at end of session may have given subjects a negative feelin g towards UNIX.