What are the rules on subject verb agreement?

What are the rules of subject verb agreement with indefinite pronouns?

• Answer:

  Indefinite pronouns One - singular You (in the sense of one) - singular or plural They (in the sense of a remote, unspecified 'authority') - plural The use of you and they as indefinite pronouns is usually colloquial, though it is very common in sentences like They are digging up the road again. To say the highway authority instead of they is generally pedantic. The pronoun one should be use as little as possible. Avoid sentences like One must avoid a situation where one does not know what one is doing. Such sentences tend to be convoluted and few people can handle them well,