After г, к, х, ж, ш, ц, ч and щ, write -у instead of -ю, and -а instead of -я.
This rule comes into play frequently with second conjugation verbs. Compare the endings on говорю́ (regular ending) and спешу́ (spelling rule), as well as говоря́т (regular ending) and спеша́т (spelling rule).
After г, к, х, ж, ш, ч and щ, write -и instead of -ы.
This rule comes into play frequently with both nouns and masculine adjectives. Compare the ending on the nouns чемода́ны (regular hard-stem ending) and уче́бники (spelling rule), as well as the adjectives ста́рый (regular hard-stem ending) and ру́сский (spelling rule).
After ж, ш, ц, ч and щ, write -о only if it is stressed, otherwise write -е.
This rule comes into play mainly with adjectives and the instrumental case of nouns. Compare the ending on большо́е (stress on the vowel following ш) and хоро́шее (no stress on the vowel following ш). The rule can also be seen clearly in the spelling of the adverb хорошо́. Other adjectives where thus rule comes into play are ста́рший, мла́дший and бы́вший.
