When hoisting a flag that is to be flown at half-mast, it should first be raised all the way to the top of the pole, and then lowered. This tradition stems from military protocol so that those observing the flag will see it being intentionally lowered (rather than failing to be fully raised)
Likewise, when the flag is to be lowered or taken down from the pole or mast, it should first be hoisted to the top of the flagpole, it should then pause for a moment, and finally be lowered, to half-mast or removed completely.
There is some disagreement about what is meant by ‘half-mast’. Most people take the phrase literally and position the flag around halfway down the structure. However, others recommend that a flag should only be lowered by one breadth - or width – of the flag (the length of the longest edge). At Flagmakers and most British institutions we recommend that the flag should be lowered to approximately a third from the top of the flagpole, This is visually easier to judge than the other two methods and leaves the viewer in no doubt that the flag has been deliberately set at that height.