In Chóngqìng or Yíchāng, most hotels, hostels and travel agents can sell you a trip on either the luxury cruise ships or the ordinary tourist boats. In either city, passenger ferry tickets have to be bought at the ferry port ticket halls, which also sell ordinary tourist boat tickets.
The price of your ticket will include the one-hour shuttle bus ride to/from the old ferry port in the centre of Yíchāng from/to one of the two newer ferry ports, about 45km upstream, where almost all boats now leave from or terminate.
Travelling With Hostel mostly sells tickets for the ordinary tourist boats, but can arrange luxury cruises too. Helpful and excellent English skills.
Harbour Plaza Travel Centre specialises in luxury cruises, but also sells ordinary tourist boat tickets. Staff are friendly and speak OK English.
Chóngqìng Ferry Port Ticket Hall is the cheapest place to buy ordinary tourist boat tickets, and the only place that sells passenger ferry tickets; no English is spoken.