The 10-Day Devotion to the Holy Spirit is a long-standing custom in the Church to prepare for the descent of the Holy Spirit in the best possible way.
Blessed Alvaro del Portillo tells us that "precisely because the Third Person of the Blessed Trinity is the one who is invoked the least, the Founder [Saint Josemaria] had a special devotion to him. I can say unhesitatingly that, in his preaching, he was a great herald of the Third Person of the Blessed Trinity. He often told me that ever since 1926 or 1927 he had practiced the devotion to the Third Person of the Blessed Trinity very intensely. Every year he followed the Novena to the Holy Spirit using the book by Francisca Javiera del Valle."
Some resources for growing in devotion to the Holy Spirit: