How to Start
You will need to know what hardware you are using. Don't despair, we can walk you through this. The easiest way to find out starts with getting a Gentoo LiveDVD. Gentoo has two versions, one for x86 processors, and one for AMD64. So, which do you need?
x86 - for any PC, can be used for newer PC's as well. Can also be used for most Macs made 2006 and later.
AMD64 - for newer PC's that have a 64 bit processor (whether AMD or Intel). If in doubt, you can still use the DVD for the x86. Use the AMD64 Gentoo Live DVD only if you are sure you have 64 bit processors, or if you have a multiple cores (Intel core duo, quad core, AMD dual core, etc.). All multi-cores are 64 bit.
Other - if you don't have a processor with Intel/AMD PC architecture, such as a RISC or a MIPS, you will need to find a way to run Linux on it. <links needed>
Download the ISO image. You can download this in any OS (Windows 98, XP, Vista, 7, 8, Mac, Linux, BSD, etc). The important thing is that you have a DVD Burner utility to burn the image onto a DVD. In Windows XP and later, you can let Windows do it instead of running a separate burner utility.
http://www.gentoo.org/news/20120401-livedvd.xml has links to the installation media, and more information. Or you can go straight to the media:
Select the one that ends with .iso. The CONTENTS and DIGESTS versions are for <what the heck are they for, anyway?>
Download the image to your favorite downloading or DVD burning directory.
Burn the image onto the DVD.
Once you have finished burning the DVD, you can put it into the DVD reader of the computer you are going to load Linux on, and start it up.
Continue at Starting the Gentoo LiveDVD
But I don't have a DVD burner! Other installation media options
But I don't have a DVD reader on the computer I want to put Linux on! Other installation media options