How to get Xcode to show its startup screen again?

When I started Xcode I always got a screen that let me choose which project to open, or to start a new project, or a few other options. A few days ago I noticed it had a checkbox that was prechecked that said something like "Always show this screen on startup". Unfortunately, I unchecked it. I thought it would just reopen the last project I was editing but that's not what it does. Now Xcode just launches without opening any window at all so you have to go into its File menu, choose open, and find your project. I want to go back to the previous (default) behavior but I can't find any way to go back.

Does anyone know how to get that opening screen to show again? (It's not in preferences.)

From Xcode 4 and above versions, it's "Window" -> "Welcome to Xcode (⇧⌘1)".

On the older Xcode 3, it's "Help" -> "Welcome to Xcode".

If you want to see the window every time Xcode starts, please tick "Show this window when Xcode launches":

Beware that you need to hover over this window to see this checkbox.

Step 1
Start Xcode, go to the top navigation bar called Window, click on Welcome to Xcode it will show you the project screen:

Step 2
Look at the bottom of the welcome screen, there will be "show this window when Xcode launches", tick it: