I decided to travel to Iran and use the train for going to different cities there. For booking tickets, would you recommend local websites or international ones?
As usual the man in Seat 61 has some useful advice on his page for Iran
Specific advice about buying tickets for travel within Iran is contained further down the page.
The best option seems to be to buy from alocal travel agency in Iran as the online sources have had mixed reviews. buying at the station is possible but you may need to buy several days in advance.
If you make the trip I am sure he would welcome feedback as it is still a difficult destination for many travellers outside organised tours.
Local person here.
In here we prefer to buy tickets from our local websites because you can get huge discounts from them.
Websites we trust with PROS/CONS is:
https://www.alibaba.ir ( Lack of English site but they have good support )
https://www.raja.ir/ ( its the official website to buy ticket but still lack of English website )
If your looking for Charter (discounted) trains go to https://www.tcharter.ir/en#!all, they have English website too.
There is a lot of websites in here for selling those tickets but not trust-able.
You're providing very little context for your trip, so, I'm making the assumption that you're reasonably flexible and don't have a specific itinerary in mind.
If that's correct, in your position, I would buy tickets locally, in-country. It's easy, as cheap as it gets, and allows you to change your plans as you see fit.
Thanks for all your information. I have recently found that website http://iranrails.com a very useful and reliable site for buying train tickets of Iran railways.