From wikipedia,

Dungeon Crawl Stone Soup is a roguelike game where the player creates a character and guides it through a dungeon, mostly consisting of persistent levels, full of monsters and items, with the goal of retrieving the "Orb of Zot" (a MacGuffin) located there, and escaping alive. To enter the Realm of Zot where the Orb is located, the player must first obtain at least three "runes of Zot" of the 15 available; these are located at the ends of diverse dungeon branches such as the Spider Nest, Tomb, and Slime Pits.

In a nutshell,

Navigate around, find weapons to [w]ield and equipement to [W]ear. Scrolls can be [r]ead and potions [q]uaffed.

Definitely familiarize yourself with how to attack, throw things, shoot spells, go up and down stairs, etc. You can bring up a command key menu in game by typing [??], there's an image of it here.

[ctrl-o] to see what dungeons and altars I've found

[ctrl-x] to see what's all in sight. for monsters this can be a quick way to select one and then press v to describe

Here's the dungeon order via hyperelliptic:

D:11 → Lair → D:12 → Orc → D:15 → S:3 → maybe other S:3 → get both S runes → maybe Elf (but not the Elf:3 vault) → Vaults:4 → maybe Crypt → Depths:4 → Vaults:5 → maybe Slime → Zot ("S" means Shoals/Snake/Spider/Swamp)

And here is Bcadren, which is an extended order and ignores Dungeon levels:

New Order: Orc, Lair, S:$, other S:$, Slime, Elf, Vaults:4, Crypt, Tomb, Depths, Vestibule, Zot (Clear for XP and so it's cleared), Hell Branches, Pandemonium, Abyss (if it wasn't done earlier when abyssed or something), Vaults:5, Orbrun.