HI! Congrats! September is a very nice time to go to WDW! You can book anytime you like. Do you have a good TA? The 2006 rates haven't been released yet but you can book and deposit without a rate guarantee. I would keep my eyes open for any specials Disney may release and watch for AAA discount released on these boards. There is no guarantee of discounts.
I would strongly suggest a college of disney knowledge graduate TA. That way he/she can keep a look out for you for good rates, etc. Booking for yourself is very easy though. Have you gone to the disneyworld.com web site and registered? Do that and you may get an email discount pin code! Also order their dvd if you haven't already done so.
You can pm me if you have any specific questions about booking for yourself.
Have agreat day. And have fun planning!