If you are a fan of bullfighting, make sure you visit Seville. The locals are the most passionate fans of bullfights. La Maestranza bullring is one the most famous sites for a corrida, so it's a must visit if you want to get a true cultural experience.
La Maestranza bullfight season usually runs for between late March and early October, so you'll have plenty of opportunities to watch a corrida. The most exciting bullfights with the most well-known toreros take place during the Feria de Abril. So the best time to witness the bullfights would be April–May (check the dates of the Fair). It is rather hard to get tickets for this event, it's best to purchase them online in advance.
While purchasing your tickets, remember the bullring has three areas. The best one is the shaded area as it offers comfort throughout the entire show. The sun and shade area is less desirable, as you'll be exposed to the sun at the beginning of the corrida and then in the shade as the show proceeds (or vice versa). The least favourable choice, particularly in the summertime, is the sun area, it means you'll have to sit in the heat for quite a while. An average bullfight session lasts from an hour and a half to two and a half hours. Usually, they start in the late afternoon, between 5 and 7 pm but it's still quite hot outside.
Also, if it rains, the show won't be cancelled unless it rains cats and dogs. However, umbrellas aren't allowed in the bullring, to not hinder the view to the others. If it's likely to rain, bring your raincoat.
Lastly, don't forget to come on time, preferably 15 to 30 minutes before the bullfight starts. You won't be able to enter the bullring when a bull is out in the arena.