what is the secret to snagging a treasury?
You can do a few things. Go to craftpolis (http://www.craftopolis.com/#com=sl)
Find out when the treasury is coming available. After you find the right time, go approx 30 minute before it's open and wait. Don't refresh your page, just wait for the numbers to drop.
In the mean time you can create a sketch of your treasury here http://www.etsy.com/poster_sketch.php