How to recompile ubuntu kernel

[Paco Ros]

Hi.

I'm running 2.6.8.1-686-smp kernel anf I'd like to compile a new one removing 
some things I don't use and targetting P4 CPU to optimize.

I've always compiled a kernel without initrd image, but I like very much this 
way to load and unload modules (and I don't remember what options I should 
compile into the kernel :-))

How do you create these kernels with initrd images? I've found some info at 
Google, but I don't know what I should put into a initrd image.

Regards.
-- 
Paco Ros