My first 5 points to remember ... when playing in a band

1. Play in Tune.. for guitar, bass, horn section, string section and even keyboards, please make sure that your instruments are in tune and on the same key. I highly recommend that everyone get their own tuner and make it a habit to tune your intruments before the performance. Vocalist listen and make sure that you are also in tune when u sing. Korg CA-40 Large Display Auto Chromatic Tuner

2. Play in sync and on time.. during your personal time, every band member should practice with a metronome. This develops internal time and everyone can eventually play in a groove. **Note: DRUMMERS are the time keepers if they cannot keep time they should not play the drums. I suggest that the drummer use a metronome during band practice.
DW Drum Workshop Complete Deadhead Pad Set with Bass Drum, Cymbal, and Head Pads

*a tight and in tune band sounds great than a complicated out of tune/out of sync band.

3. Listen to each other.. rhythm section listen to the drummer and keep stage sound down just enough to hear everyone.. drummer needs to keep his volume down to be able to hear the bass and vocals. If you cannot hear each other that means someone is playing too loud!  Parker Fly Signature Series - Adrian Belew - Electric Guitar (Tangerine)

4. Use the mic and hold it close to your mouth. Vocalist must hold the mic on its handle and avoid covering the head (this will cause unwanted feedback) the vocalist should also be able to listen to their voice through the monitors. Shure SM58LC Cardioid Dynamic Microphone

5. Come to practice PREPARED and know your parts!

The next 5 points will be for next week :)I hope this helps to bring your band to the next level.