Over the last two years, I have traveled quite a bit to speak for churches, conferences, and mission endeavors. Because of that travel, I have the opportunity to observe worship leaders in various settings. Though I'm no expert in music, I can (like you) spot when it isn't going so well.
Now, I'm no musical expert. But I'm a guy who loves to worship. So, I've assembled some simple advice for worship leaders (no matter the style of your service). Please keep in mind that these are one man's hopefully helpful suggestions.
1. Just sing the song.
Improvisation is great, unless you are leading others in singing. Then you just confuse everyone. Part of the genius to the hymns written in times past is that everyone knew the tunes to the music. The majority of people do not read music now so melodies need to be familiar.
The use of video screens in worship is helpful and appropriate for our technological context, but as a result we only focus our attention on words. Consequently, we have memorized the songs as they are most commonly sung. If you take off on a vocal riff, we don't know what you're doing and just wait for you (now singing a solo) to be finished.
2. We don't sing La-La-La
For some reason, songwriters will substitute words with Ooh's, Aah's, and La's of different progressions and combinations. Though it may sound really cool on the radio, most of us just feel stupid standing around singing La-La-La-La. And, anyway, it doesn't feel like worship when I'm just cooing like a baby at God.
3. Open your eyes.
Keith Pipes - a good friend and worship leader - once described to me how odd it is for a worship leader to sing to God but look at people. I get it. But if you keep your eyes closed during the entire music set - it's creepy.
But more than that, it tells the worshipers that you don't really care if they are participating or not. Yes, it's hard to sing to Jesus and look at me, but all of spiritual leadership involves a certain level of earthly awkwardness.
4. Stop singing in the key of "Tomlin."
Let me say it plainly: if the worship leader is singing toward the top of his/her vocal range, then you have left everyone behind about seven bars ago. If you can sing like Jason Crabb or Chris Tomlin, that's great. For you.
Speaking on behalf of the guys... Most men are baritones. They need music to be easy, middle of the road. From a guy's perspective, we will more likely not sing than squeak like we've re-entered puberty. So, when you lead worship songs in a key only fit for professional singers, most men will simply not sing. I know because I look around while listening to you sing.
5. We only know 4/4 time.
Though we really enjoy hearing the David Crowder Band sing in their odd syncopated beats, none of us can actually keep that rhythm with David. Please keep it simple for us. Again, the brilliance of the hymns is that they were easy to sing. The simple music was contextualized to the style of their day. And, it has helped them stand the test of time as accessible to the masses. Lead music that we can all sing easily so the focus is on the content of the words and not trying to keep the beat.
6. Plan the transitions.
Just like you don't like to see the preacher flounder for a transition between points, we feel the same for you. I'm not advocating a mini-sermon between songs, but at least have a plan. Hopefully, you and the speaker know what the theme of the service is to be, so speak about it in such a way that it values the scriptures and continually points us to Christ.
7. Turn up the lights.
OK - maybe this is more pet peeve than anything but here goes. I can sing by myself in the car, at home, etc. Only once (maybe twice) a week do I worship with the community of faith. But, when the lights are turned down in order to highlight the cool set, Gobo lighting effects, and newest ProPresenter backgrounds, then I don't know what the family in the row in front of me is doing. It's not that I need them to do something in order to worship, but--I think--God intends for me to worship with them. I shouldn't have to use night vision goggles to see them.
8. Dress like it is worship that matters.
Leaders need to contextualize, but only to the point that you blend in with those you are seeking to reach and lead. For some reason, those of us on the platform (preachers included) feel the carnal need to be the coolest/best looking in the room. Thus, Target and Macy's is making a mint off of ministerial professionals buying shirts with graphics emblazoned across the shoulders. But that is not the definition of contextualization. Don't try to be the grungiest one who is "free" to wear blue jeans and go bare foot in church. And don't try to be the sharpest dresser just because you are "up front." Instead, be driven by the mission of who God has given you to reach and lead.
9. Love Jesus more than music.
All leaders face the temptation to love their work for God more than God Himself. It is our own temptation toward idolatry. To speakers, I would say that they should love Jesus more than their words about Him. For worship leaders, love God more than the music about Him. No matter what else happens on the platform, it will be obvious where your passion rests.