Bus travel might be not the easiest task back in the United States due to the lack of reliable and convenient options, but in many other countries, including Mexico it's a very convenient and efficient way to travel short and long distances.
Extensive toll-road network all across the country stimulates bus travel and the first step is finding a nearest bus station nearby your location in Mexico.
Bus stations could be called as:
Central de Autobuses de [city name]
Parada de Autobuses
Terminal de Autobuses de [city name]
…and other names, but you get the idea
Selecting and purchasing a bus tickets
The second step is finding out if there is a bus stop in your point of destination and choosing a bus line that you will use for your travel.
Since there are many bus lines in Mexico (PrimeraPlus, ABC, ADO, Omnibus, etc). I recommend using an aggregator like Reservamos.mx for finding a schedule that fits your needs and even purchasing the tickets itself.
Booking through Reservamos.mx
Since the website is not in English, but in Spanish let me translate a few words, that you need to use it:
Origen - Origin where are you starting from
Destino - Destination where are you going to
Salida - When are you leaving?
Regreso - When are you returning?
Pasajero - Number of passengers
Buscar - "Search" button
Mexican bus line selection page
Eligir - Select
Final step: Payment
All is left is a final step - paying for those tickets. As you can see, there are many options and the schedule looks convenient with so many bus lines available. Once you select "Elegir" you will be presented with the options to pay. The problem here is the most bus lines do not accept foreign cards, so you would need to use a PayPal option, which usually works universally. Also, if payment through Reservamos.mx doesn't go through, you can always use a bus lines website directly and book through it. Once you have paid through a website, you will receive tickets on email as usual and the only remaining thing would be boarding the bus.
Oh, and if an electronic payment fails you can always go to the bus station and buy tickets physically. The only thing you need is some basic Spanish to communicate through your needs, so here are those magic words that you need:
Quiero un boleto para ambas direcciones - I need a ticket for both directions
Quiero un boleto de ida - I need a one-way ticket
Quiero un boleto a la [city name] - I need a ticket to [city name]
¿Acepta tarjetas de credito? - Do you accept credit cards?
Quiero dos boletas - I need two tickets
¿Cuándo es el último autobús a [city name]? - When is the last bus to [city name]?
Un boleto para el último autobús - A ticket for the last bus
Knowing those phrases will help you buy your tickets and enjoy your time at the city of your destination.¡
A typical view from the inside of a Mexican bus. Comfortable and clean!