How can I make my own linux distro?

Im 16 and a relative noob to this. I usually run Mandriva/Fedora/PCLINUX/Slackware. However, I managed a basic gentoo install and know my way around tools like vi, the shell and gcc and thaught how great would it be to make a new distro?

I justto build the OS from scratch (source) with kernel 2.6.x, Xorg, GNOME and some basic tools and acpi, alsa etc... and optimise it to run on my PIII M

Can anyone advise me how?