What are the rules for casting pointers in C?

K&R doesn't go over it, but they use it. I tried seeing how it'd work by writing an example program, but it didn't go so well:

#include  
int bleh (int *); 


int main(){
    char c = '5'; 
    char *d = &c;

    bleh((int *)d); 
    return 0;  
}

int bleh(int *n){

    printf("%d bleh\n", *n); 
    return *n; 
}

It compiles, but my print statement spits out garbage variables (they're different every time I call the program). Any ideas?