Train from Valencia to Barcelona

Use www.renfe.es, the spanish national operator.

When planing the trip just use "Valencia (Todas)" and "Barcelona (Todas)" as origin and destination. "Todas" means "all" in Spanish, and the system will select the best station for you.

Note that schedules are not yet published beyond mid December, so if your travel is after that you will have to wait a bit.

Back in 2017, I actually took the bus from Valencia to Barcelona airport though it did go on to Barcelona city centre. It was 3 hours (to the airport), comfortable, cheaper and beautiful scenery. ALSA Bus Line.

We are doing the opposite bus ride-from El Prat to Valencia. My understanding is that the bus departs from terminal 1 at the airport. I'm presuming that the signage in T1 easily directs where to catch the bus. Any quirks I need to be aware of?

@Phil H. Good question. I was more concerned getting my way to where to get my hotel shuttle, and it has been a few years. But like any airport, there are bus signs.
I often go to YouTube to see if i can get videos of the route. There is one from Valencia to Barcelona so that may help. Also a quick search says that stop is highlighted with images on the Alsa website.

Took this train journey last winter. We walked 30 minutes from the hotel to Barcelona Sants station and had a light breakfast on the way. The station was a little crowded and chaotic but just go with the flow. No problem. I bought the train journey tickets in advance and printed them out. This was the fast Renfe train service.