Level 2a: Kernel
After the hardware level, there needs to exist something that can then access those resources in matter which they can be used by your applications. That is exactly what the kernel does, it serves as the central component of the system level (level 2), bridging the divide between hardware and applications so that your device can do all the cool stuff it does. The kernel is an integral part of any operating system because it is the only thing that can provide the lowest-level of abstraction when trying to access the available hardware resources, therefore making modifications to the kernel would prove to be the second most beneficial component one could tweak; rendering the most noticeable/significant effects (well… after modifications to hardware level… but you knew that already ).
So what are the ways can we improve overall performance on the kernel level???
If you are on a Droid-x then as of today you can’t
Sorry. I don’t like being the one that delivers bad news, but unfortunately for Droid-X users due moto’s locked bootloader policy, they have essentially locked us all out of the most valuable component of the computer technology we purchased. MOTO FAIL!  Sign the petition to get in unlocked:  Let your voice be heard. Even if you haven’t rooted yet, this locked bootloader policy is holding all development back. Please take the two seconds to sign: Motorola Locked/Encrypted Bootloader Policy | groubal complaints
If you are on a super cool phone like the Samsung Galaxy Nexus then you can flash custom kernels.
Custom kernels are often bundled in custom ROMs, and can be flashed in CWM recovery. Â Alternatively if they come in boot.img format they can be flash them with fastboot (or with my Toolkit).