How to completely Fuck Shit Up audio tech wise

I have consulted with a complete sound n00b on what she would like to know regarding learning about audio tech.
Her response was perfect:

"I'd like to know, to what extent can I actually fuck shit up audio tech wise. How can I know what to do if I don't know what not to do?"

That was the best answer I could have hoped for, because we will make this fun. Time to make the worst gig imaginable. We will be following Voldemort and Mr Bean's illegitimate child who went on to become the evil and clumsy Sound-Guy Mr. VoldeBean:

He is out to ruin everyone's night.

So, how bad can he make the night. The first consideration is going to be safety VoldeBean likes his Buckfast in pitchers next to all the equipment, not only is he going to be too drunk to function, but his drink is likely to spill. If the drink spills on the mixer, the sound may cut out, if it spills on high power equipment, he could get an electric shock, a buzz stronger even, than his Buckfast. 

Don't be him and keep your drinks off the mixing desk.

Let's skip back, nothing whatsoever has been set up. So Mr. VoldeBean has to set the P.A up, all by himself. He switches everything on and turns up all the volumes first and then proceeds to plug everything in. With every plug comes a loud pop and each speaker cone tears from the force. The gig is ruined, the speakers are blown. He should have made sure everything was off and all the faders were down before plugging everything in. Even plugging a wire in can send a signal to the speakers, so will turning on the mixer, especially if there is an input already running into it. The rule is power remains off until everything is plugged in, then start powering from the source (mixer) down to the speakers. If the speakers are powered last, it means they won't blow from any powering on further back. VoldeBean ruined the night.

Don't be him, plug and power wisely.

In a similar vein, in between acts, lead guitarists need to unplug their guitars. This will have the same effect as above. Mr. VoldeBean is always away with the fairys and forgets to drop the guitar faders when the guitarist unplugs. Often this will lead to a loud band and annoy everyone but this gig is loud and now people have no eardrums due to the pressure wave.

Don't be him and drop the faders when the guitarist unplugs.

Music is great loud, and everyone knows it. Especially our talented sound guy. Volume up, Input gains up, everything up. Bass EQ at max. Even the lights are red from the awesome volume. His soft acoustic guitar is driving like a Black Metal anthem and his soft angelic voice rougher than the feel of sandpaper toilet roll. He's rocking harder than a metal oompa-loompa!

For reference: A rock oompa-loompa

The sound is horrible, the venue empties as nobody can stand the sound and money is lost. Well done sound guy. Even if the master meter lights are all in the green, doesn't mean the individual channel's aren't saturating. A quick check is done by PFL (pre fade levels) which shows the particular channel input volume on the VU meter as opposed to the master. All channel PFLs should all be green or at worst, yellow otherwise the master headroom makes no difference. If it is clipping, turn down the input gain so when the fader is at max, the sound is just below clipping level.

Don't be like him, check your levels.

VoldeBean thought the solution to volume would be playing the speakers into the microphones to be amplified again and therefore the event would be louder. He positioned all the singers microphones in front of the speakers so they fed straight into the mics. Horrible feedback ensues, the P.A screams and the crowd screams in agony with it. He tries to boost the volume so the music cuts through the feedback but it is only made worse. Worse still, he decided against soundcheck so all these issues happen live and there is no way of solving them.

Don't be like him, check for feedback and sound issues during soundcheck.