Should I just shampoo or do more?

Hi all,
I just recently got a cat, an adult one that was a stray. I took him to the vet and he got his shots, and has been neutered. The vet said he had a strong heart, and his eyes are clear. (very pretty green eyes). He's all black.
My question is he has some bald spots on him, and the vet said just to shampoo him with any cat shampoo. I'm worried about his having a skin condition, although he checked out at the vets ok.
I'm wondering would any cat shampoo do, or does anyone have any recommendations of anything I could get at the drug store for him? Would I be able to find anything at any pet store, such as PetSmart or WalMart?
He's a very loveable cat, and I've named him Shadow.

Personally, I've never used a cat shampoo - I use the good quality salon shampoos (Nexxus) on my cats - and use a little conditioner too. I have (had) whites and mainly used Nexxus Simply Silver. Works good on bicolors too (black or blue/white but don't use it on reds). On reds I used regular Nexxus shampoo.

I recommend a medicated shampoo. I bought mine from Chow Hound.

I would use human over most cat shampoos I use a all natural that I use the dog uses and if needed cat s will use... talk to the vet and read labels..