Mexico is a big country and buses are a very common way of travelling between states and different cities. If you have the time and also want to save some money, you'll choose travelling by bus over any other option and this will make for a more interesting trip as you'll meet many more people and see much more of the country. But which bus company should you use? There are different bus companies operating in Mexico, some are more wallet-friendly than others with varying degrees of comfort obviously.
The company I want to tell you about is in my experience the most comfortable, efficient and safe.
This company is called ADO buses (pronounced A-D-O).
ADO mainly covers the southern states of Mexico (i.e. virtually every southern state past Mexico City - Yucatán peninsula, Quintana Roo, Yucatán, Campeche and Chiapas). They also operate many bus terminals which are called 'central de autobuses ADO'. In places where ADO does not operate, they tend to outsource other companies such as OCC in the state of Oaxaca, which isn't as comfortable but still is good enough. You can book bus tickets for ADO buses through the company's website. I actually had an issue with some tickets I purchased online that didn't get to my inbox. I basically thought that was it and I'd never see my money or tickets again, but to my surprise, I called their customer service, and they were very professional, not only did they offer both help in English as well as in Spanish, they sorted the whole thing out in a couple of minutes.
A little tip is to always download the PDF ticket after you've paid for your ticket online if using ADO Buses. You also won't be able to create an account online if you don't have a Mexican mobile number but that should be fine as you can buy your tickets without actually registering as a member of the website. You don't need to print your ticket either, as showing the PDF version of it on your mobile before getting on the bus will suffice. Most ADO buses will have free Wi-Fi available on-board, toilets, air-conditioning, power outlets, TV and padded reclinable seats.