Everyone seems to have covered your question. I would also suggest to add yourself to the Starwood RSS for special offers, which will included double points or more. (posted to Starpoints)
Your question can be answered several ways: You would make a reservation for a normal room and receive an upgrade to a suite as a platinum member, if one is available. Or as an SPG member you can go to (posted to upgrade)
And don't forget to take advantage of the 5th night free on most SPG awards, it's almost like earning points. (posted to Starpoints)
You can buy points from Starwood for $35 per every 1000 points. Also, if you gain platinum status, you get 500 points per stay. There are also offers for bonus points per stay often offered by Starwood that you can (posted to Starpoints)