Russian Capitalization Rules

Capitalize days of the week and names of the months?

No.

Capitalize nationalities and languages?

No. E.g. американец - an American, француз - a Frenchman, русский язык.

Capitalize adjectives derived from proper nouns (containing the suffix -ск)?

No. E.g. московские улицы (the Moscow streets), парижское кафе (a Parisian cafe). Except when forming a proper noun: улица Московская (Moscow St.), Казанский вокзал (Kazan Railway Station).

Capitalize the pronoun я?

No. Only at the beginning of a sentence.

Capitalize compound proper names/titles/holidays (e.g. Black Sea, Atlantic Ocean)?

Only the first member is capitalized: Чёрное море - Black Sea; Атлантический океан - Atlantic Ocean. Except, when the second member is also a proper name (Южная Америка - South America) or referring to high-ranking agencies (Верховный Суд - Supreme Court; Совет Безопасности - Security Council).

Capitalize вы?

Yes when used as a pronoun in correspondence, but no when used as second-person plural. Also, Вас, Вам, etc. are capitalized.

Capitalize simple, one-word, proper names (e.g. Pushkin, Moscow)?

Yes.

Capitalize words at the beginning of a sentence?

Yes.

Capitalize countries?

Yes. E.g. Испáния, Амéриса.

Capitalize possessive adjectives (containing the suffix -ин)?

Yes. E.g. Катина книга - Kate's book, Сашин телефон - Sasha's telephone.