How to get a 'soft', dreamy effect in photographs?

i have a nikon d5000, but even when i change the settings, my photos don't come out 'soft' enough like these examples. They just come out like the average photo. Is there some trick?

These days you use an editing program to add blur, perhaps selectively, and change brightness and contrast. If you want to do it in the camera like the good old days, you open up your lens (f/2.8 or f/4) and speed your shutter so you get a shallow depth of field which you put behind or in front of the subject, so they or the background or both is out of focus and the actual settings are "wrong" for a perfect picture - under exposing the image to get that dark surround. Try some shots where you go faster and faster on the shutter. Perhaps lower the effective ISO to give you more range to speed up.

Using a lower aperture will usually make your photo lose a bit of sharpness. The 1st photo looks like it was shot free lensing, a technique that you may want to research. If you want it to look like the 2nd photo you need to use a higher ISO. Anything else such as color correction can be done in post-processing.

First, I see no 'soft, dreamy effect' in your second example. Murky underexposure and too much noise, yes, but this is more of a nightmare than a dream. The first example looks like induced lens flare, probably from the way the lighting was set up. BK is perhaps being a little harsh; photographers have deliberately softened portraits like the one in the first example since long before the advent of digital manipulation. A favourite method in the old days was to smear a very light film of vaseline on a UV filter and shoot the portrait through this. You could try this today if you're interested; with a digital camera you can see the results immediately and adjust as necessary. Just make sure you don't get any vaseline on your camera lens, though, or all your subsequent shots will have a soft, dreamy effect whether you want it or not.

Practice study practice and then you'll have your answer

The simple thing which photographers have been doing for years id to smear a very light smudge of Vaseline on the the front FILTER. NOT on to the lens itself. In the days of film, you couldn't see exactly how this would turn out but with digital you can see immediately and adjust the smear as necessary.
Alternatively, stretch a thin piece of nylon stocking over the lens.
The second shot just has a load of noise in it.probably with a very high ISO setting.