Airplanes get me to great, distant departure points, and my legs get me the ‘last miles’ to my destination. But buses and trains do most of the heavy lifting of intermodal transport.
If you grew up in the US it is hard to imagine how different the transport is in most of the rest of the world. I was used to some suburban and a very few intermodal trains. Same on buses. In all fairness there have been some new companies running some high quality intermodal bus lines, but not many. It is almost impossible to imagine traveling around the US without a car, or spending a lot of coin on taxis and private ride car services.
Now transport yourself to pretty much any other country, and the landscape changes dramatically. Some form of bus: collectivo minibus, pickup with board seats, stripped down school bus, run defined routes around the towns and cities. They may stop at regular spots, or rely on a barking teenager hanging out the door to attract, pick up, and alert the driver to stop and drop. A range of larger vehicles, from bush taxi up to double decker, four axle luxury sleeper coaches run between the towns. Similarly, local trains chug slowly through places that would not even warrant a second look, often stopping at stations barely more than a concrete slab. These feed into the intermodal system, marked by larger, perhaps even glamorous stations served by national and often corporate train companies.
Almost without exception the inter- and intra- modal stations are in separate locations, so when hand waving charade communicating with kind locals, try to be specific about where you are traveling to. Having earned experience (aka messed up a bunch of times), I make a point of scoping out my departure options in the station that I arrive at, to figure out if it is, in fact, the right place to show up at 06.00 three days hence.
When looking for schedule information, it is almost not worth researching local bus and train times. Bus stops in much of the world have almost zero signage and information. Just show up at a bus or train stop, and enjoy your waiting time reading. In support of my sincere believe that bus drivers are the actual force that makes the globe spin, ask each arriving hero how to get where you are going. Unsurprisingly there are a variety of payment methods and rules. Some systems have standing ticket kiosks at stops, most have drivers issuing tickets (exact change some places, change returned in others, cash only some, card only others). Some local systems run only on local system debit cards that are sold in limited locations (in which case I was out of luck trying to get on a bus in Antalya). Validating tickets that may be issued is also a hodge podge. Some systems require you to validate an issued ticket on the bus in a reader. Try to grock out the correct answer, and just do not get pissed off when you do it wrong and a roving ticket checker fines you €50 in Bratislava.
For longer distance travel options I rely heavily on Rome2Rio. In my experience it continues to improve, adding better schedule info and even some booking options. But as described in the Navigating page, I never bet my life on it being correct. Based on the region of the earth that I am navigating, smaller niche apps such as Flixbus and GoOpti help (and again, look for the signage of the providers, and search for an app). Many intermodal stations have a row of more or less grotty offices selling tickets to some or all of the providers.
For trains, other than Rome2Rio, I end up relying on the some good, some awful, individual company apps like ÖBB in Austria and SNCF in France. Then if you really want to be truly amazed at the dedicated and detailed research of fanatics, go to Seat61 to explain, for example, the insanely complicated way to get a seat on a train to Aswan if you are not an Egyptian national.