I find this tutorial very useful in cases where you need to post a friend's pic over the net. (Strongly suggest not to post in sgForums though) A pretty easy tutorial, simple to follow through. Effects are ok, can be easily seen through if someone knows their work.
1 : Open up an image that hasn't been retouched yet.
2 : Use the HealingBrush-Tool to edit small dots or blemishes by holding ALT and selecting a piece of clean skin and then just brush over the blemish and fix it;
3 : Once that is covered, duplicate the layer with CTRL+J, then go to Filter>Noise>Dust & Scratches and set the radius to 9 and the threshold to 0;
4 : Then go to Filter>Blur>Gaussian Blur and choose something between 2 and 5
5 : Now turn on the layer mask. Then click on the mask-icon that has just appeared next to your layer-thumbnail and press CTRL+I. Now you see that the previously done action (the blurring) is gone. It's not really gone, but masked. What you do now, is take a brush with a small size and choose the color white (or if your mask is white, choose black). Then start painting over the skin and you'll see that the blurred layer will become visible over the parts you brush.
6 : The lips are a little vague so select the lips and duplicate them by pressing CTRL+J. Then set the blending-mode to lighten
7 : Next, merge all layers by pressing CTRL+SHIFT+E and then press CTRL+J to duplicate this layer and set the blending-mode to screen, then lower the opacity to your liking...