What is a Treasury? It's simply a group of 12 items from different sellers that you think would look good grouped together. That's my definition anyway.
Why would you want to create a Treasury? The answer is that it gives you the opportunity to promote a group of items (and sellers) and perhaps (this is a big perhaps) it may get selected by Etsy to appear on the front page or be featured. You can also add one of your own items.
I've just managed to get my first Treasury so I feel justified in posting this while I still remember how to do it. Really, there's nothing to it, you just need to find out when the window will open so you can start adding the item numbers for your Treasury. This only happens when the Main Treasury hits 332 lists and Treasury West reaches 221. There are a number of factors which mean the timing for this cannot be predicted exactly but you can get a good idea and in future I will log in and get set up about 20 minutes before I think the window will open.
http://www.etsy.com/treasury.php Link to the Main Treasury
http://www.etsy.com/treasury_west.php Link to Treasury West
So, to estimate when that will be, count back 333 Treasuries from the last page (for the Main Treasury) and then click on that Treasury and find out when it expires. Allow 20 minutes to get set up and then set your alarm. It can be anything from immediately (unlikely) to a couple of days time. This is the point where I failed several times. You think you will remember to log in at a certain time and then the cat wants to be let out or the postman arrives or the bread machine bleeps - whatever the reason, you will run up to your computer and curse because you've missed the deadline and instead of seeing there are 340 Treasuries on the list and counting down, you see there are 865 Treasuries and you won't be able to try again for another 2 days!
Alternatively, I have found a clock that fairly accurately does the work for you. Go to this website: http://craftopolis.com/index.php?com=tc&user and it works it out for you.
So, there you are at your computer and the Treasury List is rapidly counting down to 333. Make sure that a) you are signed-in and b) you scroll down to the bottom of the page. Sadly, when you are at the bottom of the page you cannot see how many Treasuries are still listed but you just have to be patient. When it hits that magic number of 332 a box will open and ask you to enter the name of your Treasury.
http://www.etsy.com/shop/dragonhouseofyuen gave me a tip about adding your title. "The easiest way to fill in the text box is to type your title somewhere, then copy with you mouse and when the box opens - to paste your title in then click 'go' or whatever it is (a huge orange button to the right of the box). You have quite a few decent seconds to do this so don't panic.I used to type it in but now I c&p all the time." That was really good advice, especially when it's your first one.
As soon as you have entered your title you will be taken to a page where you can start adding your items. It's self explanatory and really you can just work your way through it. Etsy have written instructions which may help: http://www.etsy.com/storque/how-to/how-to-make-a-treasury-the-nuts-and-bolts-688/
What preparation can I do in advance? You can choose your theme, title, sub-title and items. That part is entirely up to you! There is a very useful tool called Poster Sketch which will allow you to enter the items numbers and then you can click and drag them around to see how your Treasury page will look. http://www.etsy.com/poster_sketch.php
You will need 12 items, plus an additional 3 slots are available as a back-up. If any of the items in your Treasury are sold then one of the back-up items will automatically replace the sold item.
Finally (although I'm sure there is much more I could add), I have been given a link to a useful tool that allows you to track the number of new views and favourites your Etsy shop receives. Personally, I prefer this to Google Analytics. http://statsy.org/vutrac.php This site will give you an update every 5 minutes if you wish and can also give you a history.
I do hope you have found this useful but if you have any questions then please drop me a note.