Hello,

I have a cat who is just over two years old.  He is healthy and happy but
lately, once  every three or four days , he has been throwing up a bit.  
I thought that this might be due to hair balls so have been giving him
treats which are supposed to prevent hair ballsbut thus far, they don't
seem to be working.  A few questions:  

I gather that this is a somewhat normal occurrence but ideally, how often
should it be happening assuming a healthy cat?
What are the best ways to prevent it from happening?

Also, it seems  as if my cat will fixate on one spot in which to throw
up.  For a few weeks, i would always find that he had done it in the
corner of the basement, but the last few times, he has taken to doing it
in the hallway between my kitchen and living room.  I am surprised by
this because I would have thought that the whole thing would be more
random and that I would find it in varied spots throughout the house.  
However, if he does have that much control, is there anything that can be
done to gently influence him to choose one spot over another?  If I had
my druthers, I would prefer that he do it in the basement.

Thanks,