Quick answer
Как э́то пи́шется?
kak éta píshitsya — plus how Russians spell out loud — by words, not letters
The options
Spelling out loud
Russians do not have a fixed phonetic alphabet like “alpha, bravo”. They improvise with first names and common words: Анна, Бори́с, Ви́ктор or как в сло́ве «дом» — as in the word “dom”. If you are spelling your own name, naming letters this way is the clearest option.
The questions that matter
Three ambiguities come up constantly, because of vowel reduction and the silent signs: че́рез «о» и́ли «а»?, с мя́гким зна́ком? (with a soft sign?), одно́ «н» и́ли два? (one н or two?). Asking these makes you sound like someone who knows the language’s weak points.
What you hear back
Typical mistakes
Как э́то спеллинг?
Как э́то пи́шется?
Russian uses the reflexive “how is it written”.
по бу́кве
по бу́квам
The fixed phrase is plural dative.
Check yourself
How do you ask how a word is spelled?