As referenced in Mac OS X Hints, Lion comes with a built-in wireless diagnostics application that will show you clear Signal & Noise level graphs as well as allowing you to capture raw packet data. Pretty cool (and somehow, not included in Lion’s feature list)! /System/Library/Core Services/Wi-Fi Diagnostics.app

This is in response to TAUW article: Get the “out of the box” experience with an older Mac. The above article is good, but the steps are limited to regenerating the Setup Assistant. The steps in the comments for deleting the user account are for Tiger (10.4.x) and do not work on Leopard (10.5.x), since [...]