Share and share alike: that’s the main idea behind Pinterest, the red-hot social site that lets you share your style with the world by “pinning” your favorite fashions, books, furniture, restaurants, articles … you name it.

But what if you’re not so keen on sharing your latest online finds? It is, after all, the holiday shopping season (what, you haven’t started shopping yet?), and maybe you want to keep your best gift ideas secret.

Meet Pinterest’s latest feature: “secret” boards, which let you hide any “pinned” items on your holiday shopping list from the world, or share them with just a few selected Pinterest friends.

Here’s how to do it:

• Log into your Pinterest account, hover your mouse over your account name in the upper-right corner of the browser window, then select “Boards” from the pull-down menu.
• On the next page, you’ll see all your existing boards displayed in a grid—and at the bottom of the page, you should see a new, grayed-out section labeled “Secret Boards,” complete with three empty boards. Go ahead and click one of the outlines.
• Next, the standard “Create a Board” pop-up window will appear—except in the middle, where you’ll see a switch marked “Secret.” The switch should already be set to “On.” Type in a name (like, say, “Holiday shopping list 2012”), pick a category, invite anyone else you’d like peek at your picks, then click the big “Create Board” button.
• Go ahead and start pinning—and when you do, make sure to select your “secret” board (it’s marked with a padlock icon) before you click the “Pin it” button.

Now, there is a key limitation to Pinterest’s secret boards: you can only have three of them at a time.

If you already have three secret board and you want to create another one, you’ll have to expose one of your existing secret boards. Just click a secret board to edit it, then switch the “Secret” setting to “Off.”

Before revealing a secret board to the world, though, make sure to let any other members of your board know that their pins are about to go public.

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