GNU Screen will read it's configuration settings from either /etc/screenrc, or ~/.screenrc. (The latter file takes precedence).
Here are the most important sections of my .screenrc. The complete file is also available.
#
# ~/.screenrc startup file for GNU Screen.
#
# Steve
# --
# $Id: _screenrc,v 1.4 2005/11/20 21:00:35 steve Exp $
#
# skip the startup message
startup_message off
# go to home dir
chdir
# Automatically detach on hangup.
autodetach on
# Change default scrollback value for new windows
defscrollback 1000
# start with visual bell as default
vbell on
vbell_msg "bell on %t (%n)"
# look and feel
caption always "%{= bb}%{+b w}%n %h %=%t %c"
hardstatus alwayslastline "%-Lw%{= BW}%50>%n%f* %t%{-}%+Lw%<"
activity "Activity in %t(%n)"
shelltitle "shell"
#
# Run a screensaver if there's nothing happening for a while.
#
idle 420 eval "screen cmatrix -f -o -u 10" "idle 0"