The Roman Missal #373 states: "In all Dioceses of the USA, Jan. 22 shall be observed as a particular day of prayer for the full restoration of the legal guarantee of the right to life & of penance for violations to the dignity of the human person committed through acts of abortion."  
Come to the 8:30 am Mass, pray, come for Exposition of the Blessed Sacrament, especially 7 pm - 10 pm in the Church.  Fast and/or abstain.  Do any form of penance.