Surely soon-to-be-outdated steps to take before recording a screencast (or presenting using a computer):
clear all browser caches
clear all saved form data
saves potential embarassment
also hides the fact that I've done a run-through already
clear all browser history? Sometimes might be useful.
reason to clear history: links appear as not visited
turn off all unnecessary browser extensions
people will ask you what those icons are
people will try to figure out how you work
turn off all apps that notify via Growl and whatnot
even better: turn off Growl
close all unnecessary applications
pre-load all necessary websites in tabs or windows
Maybe this should fit under the "Perfect" section.