If you have installed the kernel source, you cd into that directory. read the README. There are several make options. You perform a "make cloneconfig" to set the configuration to the current system you are running. make xconfig - This allows you to alter the configuration using X make menuconfig - same except it is for a text based menu make config - text based.
The one I use is make oldconfig.
Copy and gunzip /proc/config.gz in the top of the kernel sources (/usr/src/linux, on mine).
Do "cp config .config" in the same directory.
Make oldconfig.
This reads your running kernel and its setup and translates it into the makefiles, I believe.
make oldconfig reads the .config file that you just put in place and only prompts you for the new options. you're thinking of 'make cloneconfig' (which i believe is not in the vanilla kernel) which reads from /proc/config.gz and uses those options to build the kernel. no need to copy/gunzip the file. personally, when i build a kernel, i copy the .config to /boot/config-<kernelversion> because you can keep track of your config options thru past kernels that way. (of course, i also tend to not use the stock kernel from suse on my machines so no /proc/config.gz) -- trey