Step one: pick one sense and write it on the page
Choose one of the five senses and write it at the top of the draft where you can see it. Writers default to sight, so if you are stuck, choose smell or touch. Every image in the draft must be available to that sense and to no other.
The rule exposes how much of a first draft is visual filler. In the worked example, hearing only: nothing about the room's colour, nothing about the light, no window. What is left is a knock, a silence, and a duration.
Step two: put in a season word and take out the month
A kigo does the work of a whole paragraph of scene-setting in two or three syllables. Once a season word is in the poem, you cannot also name the month — that is the same information twice. In the worked example, October is doing the season work and radiator is doing the sound work; naming the street, the town, or the year would add nothing the reader can use.
Useful season words that are not the season's name: first frost, wasps, wet leaves, a coat coming out of storage, ice on the inside of the glass, the smell of the heating coming on for the first time.
Step three: the cut
Cut the poem into two unequal parts and do not connect them. The cut usually comes after line 1. Your two parts should be: a state of the world, and a small event. The reader supplies the relation.
The worked example's cut is implicit: the radiator knocks twice (event), and then says nothing all through October (state). Read that as one sentence and it is a complaint about a heating system. Read it as two, and it is about someone waiting for a sound that does not come again.
Run it five times, once per sense
Write five haiku in one sitting, one per sense, on the same subject. Keep them. The sense you found hardest is the one your writing has been avoiding, and the drafts you produced for it are usually the most alive of the five, even if they are the least finished.