Kernel - Build For Different Host

I want to use my Athlon GHz box to compile a kernel for a Pentium III 450 
box. Setting aside issues of compilation errors due to kernel bugs (which 
is the user's problem to work around, until the fixes are ready, of course 
:P), do I need to do anything to make it work for sure on that box, in the 
way of compiler flags? Or can I just leave it at the defaults, the defaults 
having worked every single time for me in the past (though I've always used 
the host system to build a kernel for itself). Or do I just need to try it 
and see?