I have not seen any Star Wars movies till date. I don't have any idea about the timeline of Star Wars but recently after the release of Solo: A Star Wars Story, a curiosity has been awakened in me. So I would highly appreciate if anybody can tell me the order in which I should watch these movies to get a better understanding of the Star Wars universe.
Film & TV Series Cannon Chronology Event Order
Episode I: The Phantom Menace
Episode II: Attack of the Clones
Star Wars: The Clone Wars (Animated TV Series. New Season is coming!)
Episode III: Revenge of the Sith
Solo: A Star Wars Story
Star Wars: Rebels (Animated TV Series)
Untitled Andor Cassian Rogue One Prequel (Live Action TV Series Comming 2020 Disney +)
Obi-Wan Mini-Series (Live Action TV Series Coming 2020 Disney+)
Rogue One: A Star Wars Story
Episode IV: A New Hope
Episode V: The Empire Strikes Back
Episode VI: Return of the Jedi
Star Wars: Resistance (Animated TV Series. Premiers October 2018)
Star Wars: The Mandalorian (Live Action TV Series. Premiere's November 12th 2019)
Episode VII: The Force Awakens
Episode VIII: The Last Jedi
Episode IX: The Rise of Skywalker (Released December 20th 2019)
Note that the "Episode" films are the Skywalker [family] Saga Films. "A Star Wars Story" are anthology films, but Solo might have been a trilogy. There is talk of a TV series, but nothing confirmed. There are also 2 other potential trilogies: one from The Last Jedi Director Rian Johnson and one from Game of Thrones EPs, David Benioff and D. B. Weiss. And there may be film coming from Kevin Feige of Marvel MCU fame.
I have given the chronological event order of the films, but there are several theories and/or preferences for "best viewing", as some feel that watching them in different/non event order (such as by release date), is better than watching them in event order. But since that is opinion based, I did not specify any preference, only giving you a layout to where everything is "suppose" to go in terms of the event history. You can look for opinion-based preferences by doing a Google search.
In addition there are several comic and book series. Some are tie-in material that expand on the films/TV shows.