Does anyone have tips on how to buy train tickets in Spain?

Best source for train tips:
https://www.seat61.com/Spain.htm

Seat 61 offers advice on independent agencies which sell train tickets at little or no mark-up and with websites that are easier to use than the Spanish company (and easier, too, than the Italians).

The short answer is that you can potentially save a good bit of money by snagging Promo tickets for trips on fast trains like the AVEs before they are all gone. How long the cheap Promo tickets are available depends on how soon other passengers grab them. You might benefit by reading the background information on Spanish trains on the Seat61.com website.

The cheapest ticket source will be renfe.com. Sources frequently recommended in the past (trainline.eu and loco2.com) have recently started assessing service charges, though I believe they may be relatively modest. You should at least price out your tickets on Renfe so you know what the basic cost is. You can then judge whether the trainline or loco2 surcharge is reasonable given the convenience those websites offer. By buying Promo tickets early, you will save far more money than you will lose in service fees. You can see the fare variation in action on the Renfe website. Price a few of your tickets for travel tomorrow, then for February. You'll note that there is some variation from one departure time to another. Always pay attention to the duration of the trip, because there are sometimes much slower trains running along the same route. They are likely to be a lot cheaper but may take 2.5 or 3 times as long.

Renfe.com is sometimes tricky to use, being prone to switching back to Spanish midway through an English-language transaction. Not impossible (I managed to buy a ticket that way last spring), but requiring patience. There have been references to detailed online instructions posted on this forum in the past. What I've found by Googling is 11 years old, and I'd be reluctant to count on its continued accuracy. Perhaps someone else here knows where we can find more up-to-date step-by-step instructions.

One trip you do not need to worry about in advance is Madrid-Toledo-Madrid. That fare doesn't change, so you can wait to buy the ticket in Spain. Note, though, that there can be significant lines at Madrid's Atocha Station, so you should plan to use a vending machine. I think Toledo tickets may be sold at a different counter from the one dealing in long-distance tickets, where waits of many hours are to be expected, but still I get twitchy at the thought of buying a ticket from a human being at Atocha Station. That is an experience to be avoided unless you are looking for a way to raise your blood pressure.

Two years ago we used loco2.com, and we were very happy with their service. Very easy to purchase the tickets online. They always responded promptly when answering any questions I had.

I used to swear by loco2.com, but unfortunately, RailEurope has purchased loco2 and the site no longer exists.

The first time I bought train tickets in advance, I used RailEurope. It's fairly easy to use. Next time, I will probably go with trainline.

https://www.thetrainline.com

In the past RailEurope was substantially more expensive than other options. I don't know whether that's still true, but it doesn't necessarily list all the trains, so you are selecting from an incomplete pool of possibilities in some cases.

That'd depend... are you talking fast train and/or long-distance rides? if so, purchasing in advance online, as Ann points out, might save you money. If you're talking regional or short-distance, you can't, you purchase them at the station on the day of your journey noting that you can take "any" train, I mean, these lines have a continuous service during the day, if you don't catch this one just take the next.

I don't know your age but if you are over 65 you can save 25-40% by purchasing a Dorada (gold) card in Spain. We just returned from our trip and I bought tickets for the Barcelona-Granada fast train from Renfe online a few weeks before we left and saved significantly by getting a promo fare. When we arrived in Granada, the ticket lines were very short and I bought the Dorada card for 6 Euros and the rest of my tickets for the trip. I had looked up the trains we wanted and just handed the ticket seller (who did not speak English) a list with the from-to cities, dates and times. The trains in Spain were wonderful! Have a lovely trip.

If you qualify, the Gold Card can be beneficial. But there is a catch that the discount is on the full price and sometimes there will be promo fares that are cheaper without the card. It depends on how price sensitive you are and your travel plans. If you can nail down your journeys (day and time), well in advance then promo fares might be better. But for a little more flexibility - and buying when promo fares are sold out - the card does work well. The card also gives a discount on the many railway services that never have promo fares, including local railway systems, so your itinerary matters too.

I don't think the amounts involved are particularly huge in the above promo/gold discount comparison. But if you want to save every euro cent, you'll need to research specific journeys and the do the maths (or "math").

I strongly encourage you to spend a little time reading the seat61 guide to Spanish railway travel which has been mentioned above.

Small correction to what Chris wrote - the minimum age for the tarjeta dorada is "only" 60.

I've always purchased my tickets on the renfe site. They don't accept many US credit cards. I believe it's because they require an added layer of security. For Visa it's Verified by Visa and for MC it's Mastercard Secure. It's easy to enroll but not all issuers participate. So for a couple years, I was able to use my Capital One MC, but they stopped participating, so now I have to use Paypal. The fees have been very low and it's been very worthwhile to use it to grab those big savings.

Wow. Thank you everyone for the great advice. There is so much good information here.

Fay

In October, we used Trainline to book Renfe tickets,roundtrip Seville -Cordoba. Worked great,website was all in English,no trouble with the credit card and about 5 Euros in fees. Worth it.

Buy in advance, we tried to buy rail tickets at the train station on the south side of Barcelona to visit Tarragona and waited in line for 45 minutes. The line was very long, about 15 people ahead of us. It took 45 minutes for two people to get their tickets. We gave up.

I spent 3 hours in line at Atocha Station in Madrid, which has been a nightmare going at least back to 2016. The vending machines will normally meet your needs for trips within Spain.

Buy in advance online where feasible. My experience thus far has been that renfe machines will not take US credit or debit cards. We've tried probably 7 different cards between us. If you buy them in Spain, just go straight to the ticket office. They'll have no problem with your card and they'll take cash as well which the renfe machines won't.

I recently used Petrabax which is a travel website dedicated to Iberian travel. It was much easier, for me, than the Renfe website.