singular

plural

1. The vocative is always the same as the nominative, in the singular as well as in the plural.
    
2. The genitive plural is always emphasized with a circumflex (sound drawn out, voice going up and then down again) on the last syllable.
   For all 1st declension nouns. Not adjectives!
   For adjectives the normal rules apply: emphasis on ultima (last syllable), circumflexed -ῶν, otherwise acute on penult (last but one), unadorned final -ων.
    
3. Accentuation
   Except for nominative/vocative (singular and plural) and accusative singular, all the other endings are long
   
   Which means that, for long endings (genitive and dative, and accusative plural) the penult will have to carry an acute. As the genitive form makes that amply clear, you should always learn both nominative and genitive forms of new nouns.
   ἡ ἄγκυρα, τῆς ἀγκύρης, the anchor.
   ἡ θάλαττα, τῆς θαλάττης, the sea, καὶ τὰ λοιπὰ
   
   The same happens when the penult carries a circumflex in the nominative. That circumflex will have to change to an acute as well:
   ἡ μοῦσα, τῆς μούσης, the muse
   ἡ γλῶττα, τῆς γλώττης, the tongue (a polyglot speaks in many tongues)
   

singular

plural