Watch these vids to understand the overall concept and tech skill needed to be a successful smasher in the game.
http://www.youtube.com/watch?v=4n4s5yB7ZkE
http://www.youtube.com/watch?v=xiZLs2doK8E&feature=related
http://www.youtube.com/watch?v=PFmGIOcWdsM&feature=fvw
Also practice with someone that's on your level and find out who smashes in your area. Let them introduce you to the competitive lifestyle of SSBM. Here's a pro tip. Never under any circumstances (when you're trying to improve technical skill) practice against a level 9 computer. The highest level you should practice on is at least level 4. Practicing against a level 9 will formulate very bad habits that will make it very frustrating you. Another tip is to try to practice your tech skill against a level 1. They have DI that's similar to a human's and they don't force any bad habits, as well as understanding the character's weight and basic recovery.
http://www.smashboards.com/showthread.php?t=42749
^^^ That thread will help you with the terminology as well as understanding how to play on a mental and technical level of smash.
In regards to learning how to play Ganondorf watch this vid.
http://www.youtube.com/watch?v=gDs-lPmIUec
This particular vid demonstrates the very basics of how to play Ganon at high level play, and will show you a very very useful tactic which is known as the reverse uair. Also created by the person performing the tech skill Thomas Tipman. Try to emulate everything he does in that video (tech skill wise)
Here are the top level pros you should always watch and no one else.
Linguini - Extremely technical and smart player. Knows how to handle each and every situation accordingly.
Kage - Not so good with tech skills, but his spacing and edge guarding is what makes him a top level pro imho.
Tipman - Founder of Ganondorf metagame. He's extremely technical and creative with various things.
Watch vids of these guys and try to incorporate everything they do into your own game. And if you need help you can ask around in the threads and they'll always be someone willing to help you out. I'm usually on aim, so if you need any advice and I'm on; don't hesitate to ask. If I'm not on, then I'm probably not by my comp but I try to get back to people that leave me messages. (That goes for everyone else too)