It doesn't work for every type of job but I do pomodoros with 42 minutes of work and 18 minute breaks.
During the 42 I focus on one task, close email, put phone on do not disturb, close door to office, no checking ge, twitter, fb, etc...
Once 42 minutes is up, i do whatever I want for 18 minutes. Repeat as many times as possible. My goal is to complete 20 cycles per week.