Here, I will list the essentials of retouching and some quick tips =D.. For beginers-intermediates
Again, I am not an expert so yeah............... take it or leave it! ^^

These tools are a MUST! What would I ever do without them? =]

•Blur Tool: Well obviously this blurs.... :P. Good for: smoothing skin, evening out the skin, getting rid of pimples and pores, and etc^^

•Sharpening Tool: Opposite of blurring =] Good for : Emphasizing certain parts, such as eyes hehe.
•Burn Tool: To darken little spots hehe. Opposite of Dodge ^^. Good for:if you want natural makeup colors, evening skin tone

•Dodge Tool : for brightening the little spots here and there =] Good for: evening skin color, whitening teeth, brightening dark spots

•Layers: VERY essential! Good for:blending colors, changing lighting =] Basically, you need layers in order to function retouches!

**Others**

• Curve Tool . A.k.A Ctr+M! To change lighting hehe very effective =]

• Hue Saturation . A.k.A Ctr+U! quick change of colors, saturation and light vs. dark ^^

• Color Balance . A.k.A Ctr+B! changing the colors of the picture hehe. Pretty self explanatory ^^.

I shall post some more if I think of them.........hehe.