I've been in ministry now full time for several years, and have been leading for about 4 years. I'm shocked at how much I'm still learning about it, but how much I also think all of the main ideas can be boiled down to just a few a things. So without further ado...
Things I've learned and would say I believe about leadership at a relatively young age:
1) Numbers are only useful tools for evaluation and should never be the end in themselves. Frequently, even when used for evaluation, the heart of the issue is missed completely in favor of pleasing others above you with numbers. That is to say, having respectable numbers are easier to report your bosses, even if being completely faithful to what the Lord would have you be doing doesn't produce hardly anything for numbers.
2) My level of satisfaction with what I and my team are doing is barely related to what they are actually doing and directly related to my walk with the Lord. When I'm satisfied in the Lord I'm satisfied in my team and their ministry. I believe this is at least partially related to the fact that when I'm tuned in to the Lord I'm (a) setting a good example to them for dependance on the Lord (our number 1 priority as ministers) and (b) better able to love them out of the overflow I'm experiencing with the Lord.
3) My primary role as a leader in ministry is to love the people the Lord has entrusted me with. This starts with my team, and is secondarily followed by locals involved in the ministry.
4) Calling people to better chase passionately after the Lord is one of the most rewarding, effective, and awesome ministries which can be done just about anywhere with anyone.
5) My foolish pride (not that there are other kinds... but still) is often my biggest obstacle to leading well.