I don't know what you have in mind by "the rules," but the Church has no special legislation that mentions expectations for the laity on the Sundays in Lent. The disciplines of fast and abstinence are in force on Ash Wednesday, Good Friday, and the Fridays of Lent.

If you are referring to personal penances, the Church doesn't regulate those. You can take them up or set them aside at will.

Michelle Arnold
Catholic Answers