Normally, for most saints’ memorials you would use the regular weekday Psalms from the Four-Week Psalter for all hours of the day, unless the proper for that saint specifically tells you to do otherwise.
The Psalms from the Commons of Saints are rarely used, except when specifically directed to do so, or when the feast is observed with particular solemnity (e.g., in a religious community where the saint was a member of that order, in a church named after that saint, etc.).
Actually, the guide (St. Joseph Guide for 4-volume breviary) indicates the regular weekday Psalms (Thursday Week IV) for today, the feast of St. Frances (OOR 1175, MP Ps 1178, DP 1183, EP Ps 1189).
When the guide says, for example, “MP from Com, Ps 1178,” you take the hymn from Morning Prayer in the Common (e.g., Common of Virgins), go to the Four-Week Psalter for the Psalms (with their antiphons), and return to the Common (e.g., Common of Virgins) for the Reading, Responsory, Canticle, and Intercessions. There is usually a specific closing Prayer in the Proper for the saint of the day, but if there is none (e.g., for a newly canonized saint), you can use the one in the Common.
Is that confusing enough?
