I have a background in traditional (non-computer) painting. I know a lot of these tricks, but a lot of things photoshop I do not understand yet 
ahh, then you already know the hardest stuff actually
photoshop is just a new medium
I usually start by tracing the boobs and copying them, then pasting them as a new layer. I usually make a copy layer of the background image too, so I can edit it to fit the layers above, without damaging the original if i need it again. Once i have the breasts, I'll blow them up very large, and then reshape them with the liquify tool so that they match up to the body better. Sometimes I'll do this in stages, increasing a little at a time, then copying the layer and doing it again. Mostly with liquify, i adjust the contours of the breasts to suit the size, and taper the upper breasts inward considerably to match up with the underlying image's shoulders. Often, the middle of the breasts will need a touch up too, as normal sized breasts often have a gap between them, but giant breasts wouldn't
So that can take some work... sometimes I cut the breasts separate from each other, and then move them closer manually, and just touch up the edges where they meet until they look good together without a gap. Often, I find that nipples get distorted or too blurry to fix with just sharpening, so I often use stolen nipples from a nipple database I've collected (like 200 high rez nipple images in different angles & lighting conditions). The outer edges of the boobs generally need to be given a 'harder' edge, so i use the eraser tool, in a fairly large size, at 100% and no fade... and just manually go around the breasts and clip off the 'fuzz' which you get from using the liquify tool. I usually use the sharpen filter on the breasts as well, to keep them crisp. Sometimes they get too blown up (pixelated), so i use a very faded brush tool to manually paint them in until they look very smooth with good gradients, and then use a very slight 'noise' filter to give them a bit of a jpg texture again, so they match the rest of the image. Generally 'noise' is a finer grain than jpg texturing, so it can actually help to shrink the boobs to a smaller size (not all the way to original, but smaller than final product) with the free transform tool, apply very slight noise filter, then blow them back up to final BE size. the fine 'noise' grain will look more jpg-ish then (but I do mean "slight" noise filter). I rarely use a layer shadow, but once in a while it's a quick shortcut. I dunno, there's a lot of other things too, but that's probably a pretty good summary of a basic run of the mill morph for me. 'free transform' and 'liquify', and liberal use of layers... are my 3 main things I guess. And retouching colors or light/dark to match things up, and maintain the sense of space
I don't get why this thread is called 'decadent dreams'. They are the opposite of decadent to me 
hehe, yeah I guess that could be taken wrong.
dec·a·dence [dek-uh-duhns, dih-keyd-ns] Show IPA noun
1.the act or process of falling into an inferior condition or state; deterioration; decay: Some historians hold that the fall of Rome can be attributed to internal decadence.
2.moral degeneration or decay; turpitude.
3.unrestrained or excessive self-indulgence.
4.( often initial capital letter ) the decadent movement in literature.
I was mainly going with #3, the underlined bit. But the other definitions would kinda put a different light on the thread. I guess the word comes from the same root as 'decay', so... yeah, you've got a point.
then again, i needed a 'bad'-ish word for a Bad kitty thread, and it sounded good with 'dreams'
