The Catholic Church defines Indulgences as such: 

“An indulgence is a remission before God of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian who is duly disposed gains under certain prescribed conditions through the action of the Church which, as the minister of redemption, dispenses and applies with authority the treasury of the satisfactions of Christ and the saints."

This depends on which of the two types of indulgences you want to do. If you aim for a Plenary (whole) indulgence you must consider: *1 work (various), *1 state of the heart (detached from sin), and *3 conditions (confession, communion, papal prayers). If you aim for a Partial indulgence you must consider: *1 work (various) and *1 state of the heart (contrite), both being less intense.