Keep It Simple, Stupid!
This is my favorite piece of advice with regard to Live Sound.
It also goes hand-in-hand with my other favourite saying:
Less is Best.
My point is that, the more you do in changing something,
the more likely you are to mess it up. In the area of mixing
for live sound you are asking for trouble if you use
excessive amounts of eq or effects.
Mistake number 1: drums; boosting lows & highs
by 12db and cutting mids by 12 db, a very coloured sound
with lots of “doof” & “crack” but a lot of the “meat”
(and power) in the sound will be lost by the lack of mids.
I suggest the same boosts and cuts, but at 3 or 6db, it will
be a less coloured but more rounded/natural sound.
Mistake number 2: vocals; adding too much
presence/hi-mids in an attempt to bring out clarity.
Any eq more than 3db for a vocal mic (where you are
wanting maximum gain) is inviting problems with front-of-house
feedback and you will also be emphasizing sibilance.
Mistake number 3: Too many channels going to reverb;
In my opinion only close miked acoustic
instruments need reverb: ie; Snare, toms & percussion
(such as congas). If more than half the band has reverb
on it, the result will be a big washy mess.
Mistake number 4: reverb on vocals;
use echo instead, echo is a more spacious/distant effect, allowing
the direct/dry vocal to sit forward in the mix.