Coaches, or long-distance buses, differ drastically and can be a reasonably comfortable or a very unpleasant experience. Coaches originating from larger cities on the east coast tend to be air conditioned with soft seats or sleepers. The roads are very good and the ride is smooth, allowing you to enjoy the view or take a snooze. Coaches are often a better, though more expensive option than trains.
Sleeper buses are common in China; instead of seats they have bunk beds. These are a good way to cover longer distances — overnight at freeway the speed is 100 km or more — but they are not all that comfortable for large or tall travelers. At some places you have to remove your shoes as you enter the bus; a plastic bag is provided to store them. Follow the locals. If there are food or restroom stops, you put the shoes back on.
A bus in rural China is a different experience altogether. Signs in the station to identify buses will only be in Chinese or another local language, routes may also be posted on bus windows and drivers will shout their destinations as you pass. Due to different manners and customs, foreigners may find bus personnel to be lacking in politeness and other passengers lacking in manners as they spit on the floor and out the window and smoke. The vehicle can get crowded if the driver decides to pick up as many passengers as he can cram into the bus. The roads in rural China are frequently little more than a series of potholes, which makes for a bumpy and painful ride. Scheduled times of departure and arrival are only rough estimates, as many buses won't leave until every seat is sold, which can add hours, and breakdowns and other mishaps can significantly extend your trip.
Getting a ticket can be fairly hard. Large bus stations have ticket counters who sell printed tickets displaying the departure time, boarding gate and license plate number of your bus (not always accurate) and have fixed prices. Smaller bus stations will have sellers shouting destinations and will direct you to your bus where you pay on board. Even large stations have sellers outside - generally they will call the bus driver of a departing bus, who will wait up the road while the seller takes you there on the back of a motorcycle to the waiting bus - you can then negotiate the fare with the driver.
City buses vary from city to city - generally expect plastic seats, many people, no English signs and unhelpful drivers. However, if you can understand the bus routes then they are cheap and go almost everywhere. Buses will normally have recorded announcements telling you the next stop. Some major cities such as Beijing or Hangzhou will have English announcements on some major routes. Most buses have a metal cash-box next to the entrance where you can insert your fare; on longer routes a conductor will collect fares and issue tickets and change.