Most of the times I just edit the brightness and the colour tones of the picture, and rarely will I bother with removing spots, making my hair bigger, making my nose slimmer, eyes bigger, etc. I used to, but I guess I grew out of it. If I don't like how I look in a certain picture, let's say I think it's an unflattering angle for my nose, I'll just pick another one rather than spending ages editing it.
With that being said, I hope someone out there finds this tutorial helpful!
Here you have the original picture. It was taken in Singapore last summer, but I never uploaded it. The first thing I'll do is resize it to 800 x 533, to suit my blog layout.
Image -> Image Size
2. Screen (brightening)
Normally people brighten their images using the Brightness/Contrast tool, but I prefer duplicating my layers and setting the layer to Screen. To duplicate your layer you could either right click on top of the original layer or just drag it down to the small square symbol beside the trash can in the bottom right corner. After that have your new layer selected, and click on the drop down bar where it says Normal, and set it to Screen. Then just adjust the opacity (strength) to suit your liking, which is located right beside the down bar. In this case I set mine to 71%.
One of the things you could to to change the colour tone of your picture, is to use Curves. Go to the down bar, and change between the four different options; RBG will affect the contrast, while Red, Green and Blue will change the tone. Just click on the graph looking thing, and small dots will appear. Just play around with it, and you can always adjust the opacity to your new Curves layer if you feel that the effect is too strong.
Layer -> New adjustment layer -> Curves
5. Fill layer (solid colour)
Most of the times I will change the colours using different fill layers. After selecting a new fill layer in solid colour, click on the down bar where it is now set to Normal, and change to whatever mode you like. Normally I'll alternate between Soft light, Linear light, Pin light, Difference and Exclusion. Just select one, and then play around with the colours. Usually I'll edit the opacity as well, and I'll go back to edit the opacity on the Screen layer if it turns out too dark. For this case added three different layers; Soft light, Difference and Exclusion.
Layer -> New fill layer -> Solid colour
6. Selective colour
Then you can use something called selective colour, which will allow you to edit one particular colour at the time (I'm terrible at explaining this). Just select whatever colour you like in the down bar. Normally I'll just edit the black colours in the picture, but if you like you can edit the intensity of different colours rather editing the contrast (which normally ends up looking very tacky if you overdo it).
Image -> Adjustments -> Selective colour
Now just go back and duplicate the original layer again (the one at the very bottom), select all your layers expect the original one, and merge them together by pressing Command + E. Then you can do stuff like blur out the background, sharpen the picture or add another screen layer of you still feel that your image is still too dark. For this picture I sharpened it, and added a new screen layer. And remember, you can always edit the opacity if the effect is too strong.
Filter -> Sharpen -> Sharpen
And after that you're done! On occasion I'll do other things, but this should at least get you started if you're just starting out. Good luck.