How to achieve a photo like this?

First thing - shallow depth of field indicates a good, fast & sharp lens wide open.
That alone makes here most editing unnecessary.
Second - uniform lighting, almost no shadows. Meaning - softboxes or flashguns with umbrellas (or other diffusers). Two or more.
With good lens and good light, You can get such results almost straight from camera.

 

Yeah I agree with MiQ69, no editing nessacary to get a picture like this.

It can be done with 2 sources of defused light pointing at the subject at an angle like this

 

Wow - great tips on photography and lighting!

 

If that's the technique I think it is... It's quite popular as a post-editing trick in the cosplay community. (I think it looks fake, but these are dolls now, and it's okay here XD)
Provided you don't have access to all that awesome lighting equipment, here's how you do it in Photoshop (I don't use GIMP so some terms will differ):
* Copy the image to a second layer.
* Apply a light Gaussian blur (Don't obscure too much detail.) to the top layer.
*Change the blurry layer to have a blending mode of Screen (This will lighten the colors, intensify them)
* Adjust the layer settings to taste.
* All done!
It's a type of controlled overexposure that won't blow out the whites the way a flash + small F-Stop will. It's especially ... "effective" with bright colors, which is partly why it's so widely used with cosplay photos.

 

You shouldn't need to edit the photo to get that effect. It's simply a macro-type shot focusing on the doll and a blank, blurred background. XD Here's a link to a photo that I took with the teqnique I'm about to describe. No computer editing except a little bit of playing with the light levels and a dot of white on his lip XD http://luarwulf.deviantart.com/art/Samuel-142219058

(1)Hang a sheet, or stick your doll over a foot away from a blank wall. Grab a lamp or two, so that there's plenty of light on the doll's face (other posters have gone over lighting, so I won't.) ^^ Lighting is very very very important to a photo. Make sure your camera flash is off!

(2)Set your camera to MACRO mode, zoom in a little, and then push the button halfway down until the camera focuses on the doll's face. You may have to play around with how far away your camera is versus how zoomed in, until you get it to where it focuses.

The effect should be that the background is blurred. Take lots of pictures and delete the ones that are unfocused.

 

No editing required, I have seen this done successfully in person (people, animals, etc)

 

I agree to most of what was said, though this picture was taken with just one source of light. A window, with indirect light, I guess. Other than that: wide open lens, slightly overexposed (half a stop). Maybe a little dodge and burn and selective sharpening around the eyes.