This is just a basic / simple tutorial to achieve that "dreamy" soft focus look in photographs. I usually do this in photos I take for dramatic/romantic portraits and/or wedding photos.
step 1: open the file in photoshop. Im gonna use here the photo I took for my high school friend's pre-nup shoot.
step 2: duplicate the photo in the layers palette. (select the photo then press command+J or ctrl+J)
step 3: with the duplicate of the photo selected in the layers palette, apply gaussian blur.
The amount of the gaussian blur will be tha amount of the "dreamy glow" of the photo. The sample photo here was taken using an 8MP camera. I set the blur here in 15.4 pixels.
step 4: Set the opacity of the blurred layer in layers palette. Experiment. Try what opacity level works for you. I usually set the opacity from 30% to 45% depending on how soft I want the photo to be.
step 5: create a mask for the blurred layer, then use the brush tool (set to 30% opacity) to mask out the eyes and the lips and other important highlights that you want to be a bit sharp. this will make the catchlights in the eyes and the lips to be a bit defined. don't over do it though.
step 6: now select the two layers (click the first layer then while holding command or ctrl, click the blurred layer)
and merge them (command+e or ctrl+e)
step 7: now we're gonna add a bit of contrast to the photo. duplicate the merged layers (select it the press command+J or ctrl+j)
then set the duplicated layer to "overlay" and set opacity the opacity to 8% to 15% whichever would look best.
now we have given the photo that "dreamy" soft focus look
here are the before and after photos: