write + (and…) + do in advance
kaite oku
do in advance; do and leave it that way
meaning: write in advance
飲み物は俺が買っとくよ。
nomimono wa ore ga kattoku yo.
I'll get the drinks beforehand. casual
旅行の前にホテルを予約しておく。
ryokou no mae ni hoteru o yoyakushite oku.
I book a hotel in advance of the trip. neutral