there are thousands of tutorials (written & video) on the internet. if you have a phat console, i would find out what motherboard i have, and what dashboard im running. depending on the motherboard & dashboard your console may/may not be jtag'able.
as for slim xbox 360 (its called RGH) Reset Glich Hack, but pretty much same as Jtag. see my post here to determine if your 360 slim is RGH'able.
http://www.tiaowiki.com/forums/index.php/topic,4060.0.html
my advice is to research,and learn everything you can about your system,motherboard,dashboard your using, and post Questions about the parts you dont understand. worst case: pay someone to do it for you. (if not done correctly, you'll end up with a $300 dvd/music player!)