how does understanding the worldview of other religions help you minister to other's needs?

Well I guess the most obvious way is that it helps you to know where other people are coming from. If you know nothing about someone else's background it is extremely easy to misunderstand actions that, to them, might be completely normal. Understanding their worldview helps you to know their thought patterns (sort of), and be compassionate and understanding.

Another way understanding other religion's worldviews helps is so you can find a common ground, if any exists, in your beliefs from which to start a relationship and be able to minister to others.