OK, so it's been a long time since I've been young enough to be considered a junior anything, but I still think I have some pretty useful advice for beginners and juniors who are trying to get into the game.
The very first thing I recommend for any new player is a thorough reading of the rules. I don't mean a five-minute skimming of what you think is most important - I mean a super-duper, extra in-depth reading that will allow you to play with the "big boys." After you've read the rules supplement that come with your cards, I suggest getting a hold of the current rulings documents or reading the FAQs (Frequently Asked Questions) located on the Decipher site. Before you worry about getting every single main in the game, before you start planning the world's greatest decks, before you go hang out of the Decipher Discussion BBS and ask a thousand questions, you must read the rules. It's the only way that you'll be able to understand how all of your cards work together and how you can make different strategies work for you. [While I'm on the subject of reading the rules, that's some pretty good advice for veteran players as well.]
There's a pretty good chance that you think you know the rules, but let me pose a few questions. Does it cost anything for characters to get in and out of vehicles? If a character with game text that allows it to react to a battle is inside of a vehicle, can it disembark and move to a battle at the adjacent site? Can a character attack a creature? If so, how? What does the term "cumulatively" mean? If there are two Dark Jedi Lightsabers being held by two different characters at the same site, how much is the force drain bonus at that site? What does "out of play mean?" At what point during a battle do destiny adders get played?
While some of these questions are easy, others are a bit tricky, and only someone who is truly familiar with the rules.
One main benefit of reading the rules is that you become more familiar with the mechanics of the game. Even the most seasoned SW:CCG veteran still has problems with the game mechanics that relate to timing, but even much simpler aspects of the game are tough to remember when you are just getting started. I can't tell you how many younger players I see in tournaments who have decent deck and come up with good strategies, but lose because they forget one of the most important elements of the control phase - - to force drain.
But reading the rules isn't just about knowing what you can do during a game — it's also about knowing what your opponent *can't do*. In the very first tournament game I played, a kid kept blocking my force drains by moving his TIE fighters back and forth between two systems. It wasn't until much later when I was looking through the rules for something that I noticed that hyperdrive is required to be able to move from system to system. While that's an extreme example, it really happened, and it could happen to anyone who wasn't familiar with the rules for starfighter movement.
So there you have it - my first piece of advice for young or very new players. Best of luck and keep playing.
Below are a few links that you should check out if you're really interested in the rules.
The Official Rules Supplements by Decipher
The Decipher FAQ (Frequently Asked Questions)
MG Dufresne