Epiphenom posted a great review of a 2009 meta-analysis that firmly shows that prayer for the sick does not work. So don’t waste your time. Instead, visit them, send them money, write them letters, help their families. Practical compassion helps people while kneeling, squinting and talking in your head to an imaginary spirit is a waste of time.
Source: Roberts L, Ahmed I, Hall S, & Davison A (2009). Intercessory prayer for the alleviation of ill health. Cochrane Database of Systematic Reviews (2)