It is simply a question of organising your time off. Schedule it long enough in advance so that everybody knows when you are off. Do not wait for the last minute. You are then left with the left-overs.
For my part I always take 2 weeks at Easter, 1 week in June and 3 weeks in October/November, plus a few long weekends. Everybody knows it and everything is scheduled around those periods.
I switch my mobile phone off during those times.