Ebay!
yes, best to buy what you want (resort and season)....no doubt!!!.... always has been, always will be.....don't buy to exchange, where there are no guarantees nowadays. exchanging is still fine, don't get me wrong, but don't let that be your modus operandi.
If you're an ebay newbie, start watching ebay listings....and take your time to learn and get the feel. NCV weeks are for sale often, even right now. They do command good prices, esp high season, because NCV is a great resort, BUT the prices are still FAR BELOW what you'd pay for a brokered resale. Ebay is the best source, and has been for a couple of years.
NOTE: Some weeks are listed at a set-high "buy-it-now" price....avoid these. the sellers of those are just fishing for an impulsive buyer. regular auctions beginning with a modest start price, some as low as $1, will end with a price well below those. The NCV week sales history can be looked up via a search, if you want to check past sales.
If you are not registered on ebay, do it now. and then go to "timeshares for sale" via a search. Then enter "marriott" and see the list.......you'll find various seasons of many resorts, NCV included. Be patient, and watch a few auctions for NCV before you try, and you'll get an idea about what they'll sell for. Ebay is safe.....you can check out the sellers and the closing companies.
The NCV weeks will begin with a few good bids (many will be interested), then sit totally idle a few days until right before the end, and then you'll have a mad finish in the last minute. Watch them, and also look at the final bidding prices after it's over, and see how the bids increased, and when.
worth repeating: the final selling prices will still be lower than thru others sources.
I own 6 marriotts (5 bought thru marriott years ago/mid-90's, plus one last year by resale on ebay), and also bought 4 additional non-marriott weeks on ebay. very happy with all of those.
BTW, Redweek.com has a current listing for a platinum NCV for $7,500---maybe negotiable, but you may be able to do better on ebay. see:
http://www.redweek.com/posting/R503853
good luck and enjoy NCV---it's one of my favorites....definitely one of marriott's best. traded there about 4 years ago and loved it. beautiful!