Ministering "To" someone is similar to talking "To" someone.
The person doing the talking may or may not actually being doing any good at all.
If you are talking "To/At/For" someone, do you know what they need? What they think? Who they are?
If you are ministering "To/At/For" someone, they same problems exist.
We don't want to minister "At" someone anymore than we want to talk "At" someone.
Don't minister At someone -- minister WITH someone.
(Note: I jotted this down after watching a video that my sister-in-law posted that was put out by the United Methodist Church on their new missions/ministry campaign. You can see the video here: https://www.youtube.com/watch?feature=player_embedded&v=GKBT8mV0CMc )