I use to put my headphones and have some instrumental music playing, mid-loud. Preferably some fast (but not aggressive) tunes - it feels like my brain is 'overclocked'. I don't like lyrics because I always end up paying attention to it.
Helps me getting focused, avoid distractions (by signaling to people that you're busy and concentrated AND not letting you hear external noises) and gets me an 'isolated from the world' sensation.