+100 on each point! Especially the vocal rehearsal thing. Harmonies are often what separates the men from the boys. If a band can pull off 3-part harmonies, they'll often get your attention moreso than a single vocalist. Not to discredit the great bands out there that are "one vocals" only, but in my experience people react to the fact that you've taken the time to write and arrange vocals and harmonies just as you would guitar/bass/drum/keys parts.Work just the rhythm section to make sure that's all on the money.
Have special vocal rehearsals to make sure everyone is one
with their vocal parts.
No booze until practice is over!
Turn down, listen to each other.
2. Listen to every practice recording.record every practice.