The easiest way to overclock is raise the frequency of the ASIC chip from miner command line, but in hi frequency (to achieve 2.2 GHS and more) you must rise chip voltage by soldering two resistors included in my kit. And of course you need to ensure sufficient cooling by attaching heatsink with fan, whichever I'm included too. Here you find overclocking instructions from Antminer U1 producer https://github.com/AntMiner/AntGen1/blob/0549a473dcf00a83842bb45d422b57db9f59d32d/manual/AntMiner-U1%20over%20clock%20guideline.pdf