When is Visarga used in Sanskrit?

There are few basic rules of Sanskrit grammer. Visarga ( ः ) is attached to nouns in following cases -

1. Nouns ending with A ( अ ) Masculine, eg. देव; Nominative Singular it becomes देवः, Nominative plural देवाः, Instrumental plural देवैः, Genitive and Locative dual देवयोः , etc
2. Nouns ending with आ, Feminine eg. माला, Acusative plural मालाः, Instrumental plural मालाभिः, etc
3. Nouns ending with स् ( मनस् )Neuter :- Nomimative singular becomes मनः

It is also attached to pronouns such as सः , तैः

In verbs, it will be found in present tense as P.P. first person dual and plural, P.P. present tense second person and third person dual, P.P. past tense second person singular etc.

The adjective changes according to form of noun.

For exact details, refer विभक्ती प्रत्यय ( suffix according to case, gender and ending vowel , for Nouns and Adjectives ) and धातू-काल प्रत्यय ( suffix according to tense, Pada, Number ( वचन ) for Verbs. )