You can practice all you want as a band but if you do not get the mix on stage down in each and every situation you will not come across as a tight, well sounding band. Taking time to understand just a couple of things will help you be able to make your sound out front be the best it can be.
First, hire a sound tech if at all possible. And you should treat the techie as another member of your band, not as a roadie. You are going to be looking for a person that understands live stage sounds. Not just someone who can solder wires. Just because someone understands the nuts and bolts of equipment does not make a mighty mixer he.
Next mike everyone. I mean everyone. It is going to be easy to get the drummer to go along, but the lead guitar player may have other ideas. You have to convince them that they will sound just as loud out front but be more in the mix of things. And that is exactly what we are trying to accomplish, a good mix. You will have a ton of more control if there is a mike everywhere. This may create a little feedback problem at first but you will learn quickly what instruments are problems in each situation. And every situation is different.
Try and make sure the lead guitar is loud during his lead only. Make the rhythm guitar soft to medium. Mike the bass drum and make sure the bass player is playing on the drummer’s bass. The tech should be able to pull each and every sound up or down as the song requires. Good monitors lets the musicians know what is going one. Pre-fade some instruments and post-fade others. You will know which real quick.
Above all the vocals should be out front and crisp. I love crisp. I never liked muddy vocals. People who enjoy good music like to hear the parts and understand what is going on. I am not a fan of overpowering a crowd and trying to baffle them with B.S. All and all good equipment is a must and a good tech is the key.