I work at REI, so I can help out with some advice at the least.
Have you backpacked before? If not, do some small trips first.
The two most important pieces of gear are your boots and pack. Make sure they both fit properly. Get fitted for a backpack at a backpacking shop so you know what a proper fit is. Make sure your boots have lots of support, and make sure they're broken in.
Make sure you know not only the rules, but the etiquette. Pack it out.
For peaks that high, you might want to use a liquid fuel stove, not a compressed gas stove.
Make sure you know first aid. Along that line, make sure you know how to treat blisters. One untreated blister can mean not summiting.
Yeah... see if there's a local backpacking club, like the los angeles backpackers club:
http://backpackers.meetup.com/129/ . If so, go on a couple trips with them.
My REI has free classes, like into to backpacking, preparing for whitney, and others (I teach into to bike maintenance). If you have an REI near you, go in and pick up their event schedules and see what classes are coming up.