If you configured any of the parts of the kernel as modules, install them in /lib/modules/2.6.30.1:

make modules_install

Export the kernel's header files in a form suitable for use by userspace programs:

make headers_install

Kernel version

version=$(<include/config/kernel.release)

Install Linux kernel image:

cp arch/i386/boot/bzImage /boot/vmlinuz-$version

System.map is used by module-init tools and some debugging tools to retrieve the actual addresses of symbols in the kernel.

cp System.map /boot/System.map-$version

Save kernel configuration file:

cp .config /boot/config-$version

Recreate the according initramfs:

mkinitramfs $version