Running OS X on a USB Thumb drive

Hardware: Macbook Air 3,1

USB 2.0 thumb drive

Hi, I've installed Mountain Lion onto a bootable USB. As in, I am running OS X off a USB thumb drive as opposed to the internal hard drive. I am running on a Macbook Air with USB 2.0. What are the best performance optimizations for this arrangement?

I am aware that USB read/write speeds will heavily limit the performance of the operating system. I would like to find out if there is anything I can do to make it as fast as possible given this arrangement.

I don't want to affect anything in the internal drive for work purposes.

Any tips would be much appreciated! Thanks.