Talking about normal maps... There a great tool called "CrazyBump", it's the best texture related tool I've seen.. You can load diffuse texture and it automatically makes specular, bump, normal, displacement maps... And its increadibly smart even if its "automatic", like if you put rocks it will make EXACTLY proper stone bumps, if you put bricks, it'll do bricks, a shop window... it'll do it perfectly! And no, by saying "automatically" I don't mean just make 3 more files without you knowing what it did.. You have a hundred adjustment sliders, and its not only previewed on texture (like in photoshop), but also on 3d model with lights! And the best thing is that if it's sometimes not that smart, and if your own try in PS was not enough realistic, you can actually blend the two samples into the perfect one!
And it's not only for setting up , but you can edit original diffuse as well, such as removing shading and highlights, like when you make a seamless texture and you look in game, and it actually looks very artificial cause you see various spaces lighter, and other darker, and it's very obvious they repeat.. You just move these sliders a bit... And... It's gone!!! There's no such thing in PS, and I was looking for this the whole time!
I have no idea how it works, but it's just ..... MAGIC! It saved me so much hours of work just in PS.. ...My god! I sound like a promoter! ... ... but, really, just try it, theres a trial I think, I got the full..