Professional Photo Touch Ups via Photoshop

I dunno if this topic will be popular or not but hey I'll give it a shot.

I think a lot of us here are quite well-versed with Photoshop but very few know about touching up photos, which are mainly used for magazine shoots or advertisements. You can even use such techniques in everyday photos.

So if anyone is interested, I will write a few tips or tutorials on how to do a basic touch up. Everyone is free to contribute if they have anything to share.

So, any listeners?