Here is something Gary Lamb posted on the RidgeStone Backstage blog (which is a great place to check out for guys/gals trying to do church well) on the importance of finding the right worship leader. Make sure you go read his stuff to get the full context of what he's saying.
9 Considerations When Hiring a Worship Leader
1.) Make sure their style fits your style.
2.) A Worship leader doesn’t have to have the best voice
3.) Make sure their philosophy fits your philosophy
4.) Be VERY specific in letting them know the style of worship you want
5.) Define their role
6.) Make sure they want to lead worship and not be a rock star
7.) Make sure they can lead a band
8.) Make sure they are open minded
9.) Make sure their heart is in the right place