水到渠成 Where the water flows, a channel forms. When conditions are ripe, a matter succeeds on its own. Su Shi wrote in a letter to Qin Taixu: “When the time comes, make other plans. When the water arrives, the channel forms. There is no need to worry in advance.”
瓜熟蒂落 When the melon is ripe, its stem falls away. Once the time is ripe, a matter succeeds naturally.
火候 The strength and duration of a fire. Also, figuratively, a level of attainment, or the crucial moment.
造势 To build momentum. To create a favorable situation through publicity and similar means.