This post is 100% NOT for actual sound engineers. If you're a sound engineer, please don't read this article and if you do read this article, please don't comment with a bunch of tips or be all condescending. This article is meant to help bad-sound-engineers fake their way through a mixing session.
I'm a terrible sound engineer. I think I have a decent ear for what sounds good in a band mix; I just can't actually make it happen behind a sound board. And maybe you are, too.
Real sound engineers are awesome - a gift from God - but what happens when YOU have to mix the band for a service? There are some tricks you can use to improve the quality of your mixing. This is about as basic as you can make it. You won't be as good as the guy or gal who has a working knowledge of things like mic placement and frequency range, but maybe these little tips will help you get a better mix than you might normally come up with.
I won't event talk about EQ here, except to say this: go brighter on the drums. We all love those big thick kick drums and toms, but we often end up mixing drums that are too thuddy. Even the best snare drum won't crack enough for the mix if everything is designed to shake the subs out the door. If you've got an overhead mic (or mics) on the drums, use those to catch more brightness coming off the snare and toms. You have to watch out for cymbal crashes, but it wouldn't kill the drummer to do that a little less, right? EQ and Compression and Effects are all vital, but remember...this post is for all you sound dummies like me.
Three (and a half) steps to mixing a live band for worship. I told you it was basic.
1. THE BIG THREE
Once everybody's plugged in and running a song, bring every instrument down in the house. If your team uses in-ears, this will mean a near-silent stage for a few seconds. Then mix the big three - DRUMS, BASS and VOCALS. The drums keep the congregation together. The bass communicates the root chords throughout the song - a solid foundation underneath all the harmonic variety of the rest of the instruments; The vocals lead the actual singing. Build a mix where the drums and bass are balanced and the lead vocals can be clearly heard. Once this is done, have the band run songs of differing intensity to make sure the big three have some consistency song to song.
2. COLOR IN
Now find the texture elements. These are instruments that are communicating more attitude and tone than actual rhythm. These are the electric guitars and keyboard pads. At this stage, the added instruments aren't taking away from the role of the drums in keeping everyone together. This may seem counter-intuitive; it may seem as though you need to add rhythm parts second (piano, acoustic guitar, aux percussion, etc) but avoiding them will help you to still have a strong, singular groove while you're mixing.
3. SOLO THE RHYTHM STUFF
If you're able, grab some headphones and start listening to the rhythm instruments like acoustic and piano by themselves to find out what sort of "attack" they're bringing. If they're good players, they'll be finding ways to support the tempo without mimicking the drums - they'll be playing good rhythm parts in the "gaps" around the drum parts. If they're too rhythmically busy, you have two choices. Keep them quiet or have them try a different playing approach so you can carve out some space for them in the mix.
3(and a half) BGVs
Good BGVs are amazing. When done right, they can elevate a worship set in beauty and nuance. But you have to be wise with BGVs. If the lead singer is doing a song that's hard for both guys and gals to sing unison, bump those BGVs to give the congregation some other parts to sing along with. However, if the congregation can easily sing the melody, stay busy with the BGV channel, using them as an artistic tool to add size and intensity to the songs.
You won't win any awards for mixing like this, but if you don't know much about live sound mixing, these tips will help you build a mix that will work for congregational singing.