Samsung has already begun allowing customers to reserve a Galaxy Note 9, even though the device isn't set to be unveiled until next Thursday. Interested customers can head to the link at the bottom of this post, and reserve their Galaxy Note 9 now before the device is announced. Reserving it is not the same as pre-orders. Instead, you are just putting your name down, saying you are interested in the device when it is available for purchase. Samsung will email you once pre-orders or general availability starts, so that you can make your purchase.
Now, on this same page, Samsung also confirms that it will be offering a trade-in program for those looking to upgrade to the Galaxy Note 9. Samsung's website states that you'll be able to get up to $450 off of the Galaxy Note 9 by trading in your smartphone. However, the newer the smartphone, the more you'll get for it via trade in. It also notes that if you do opt to trade in a smartphone for a Galaxy Note 9, you'll be one of the first to get the "Next Big Thing" from Samsung, and guaranteed delivery by August 24. Now while Samsung has not announced pre-orders or availability yet, that does sound like it could be the day that the Galaxy Note 9 is actually available to the general public. That's just a little over two weeks after the Unpacked event in Brooklyn, which does also line up with previous pre-order and availability time-frames for other Samsung smartphones.
If you are interested in checking out the Galaxy Note 9, and do want to be one of the first to pick up the new device, then it is definitely a good idea to reserve yours now. As mentioned already, this does not cost anything and also doesn't set aside a unit for you to purchase later on. So you'll still want to purchase one as soon as pre-orders open up, which should be within a few days of the big unveiling on August 9.