the only hard thing here is preparing the USB stick, but actually the Debian guys took care of most of the process so, here you are:
You need a running Debian system, plugin a USB stick with around 200 megs of capacity.
This steps will delete all the data from the USB stick!
Assuming your USB stick was added as /dev/sdb, otherwise change the command accordingly.
wget http://ftp.de.debian.org/debian/dists/lenny/main/installer-i386/current/images/hd-media/boot.img.gz zcat boot.img.gz > /dev/sdb wget http://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-506-i386-netinst.iso mkdir /mnt/sdb mount /dev/sdb /mnt/sdb cp debian-*-netinst.iso /mnt/sdb umount /dev/sdb
The stick should be bootable and ready now.