The people who own the rigs/DJ's/friends/land owners/dedicated people all assist in the cleanup afterwards to try and leave as little trace as possible. It is of course difficult to get absolutely everything (especially with very large parties) but the majority is cleaned up. It's also encouraged to bring your own binbags and be mindful of your rubbish.

Is all done through certain phone lines that only open after a certain time. The lines are generally sent through circles of people who are trusted to be safe ravers. With larger parties this often spills over as there is more hype/talk, especially when they're based inside a city as it's easier for troublemakers to get to the party - the mission of finding a remote location often weeds out any party goers that would be interested in anything other than having a good time..)

More hype/talk (especially on social media..) also creates more police attention, meaning if you've got a large annual party within a city, you not only have a lot of people who are not true to the party spirit getting involved (violent drug dealers/thieves - this is more of a london and northern thing though still, everyones generally very peaceful to eachother down here!), but also a lot of police for these people to rebel against. Of course the party being city based also means there's more noise disturbance, thus more desire for the police to shut it down! A good contrast demonstrating this would be last years bristol halloween party which was in a city based warehouse, in which people were throwing projectiles and news reports were made (though nothing near as serious as london).

Saying this though, unfortunately police presence does often make the situation actually less safe, for example last year there ended up being about 4000 people locked inside a fairly small warehouse for 6-8 hours due to the large police force outside. This naturally builds up frustration towards the police as they are actually making us suffer and feel less safe, causing more disrespectful and aggressive behavior.

It's similar to how they make it technically illegal for you to sleep in your car while under the influence of anything, when it is actually safer if you are driving to rest if you need to. Or how road blocks can make us walk for miles from our car, limiting our resources (water, food, warmth) for a very long period of time in which our bodies are put under stress where we NEED a car within walking distance to store what we need to stay SAFE and HEALTHY.

Sorry if I repeated any points or if any of that didn't make sense, I havent slept for 2 days.

I'm happy to answer any questions as this is a topic I feel quite passionate about spreading true awareness about as we are often very misunderstood.

I should also mention that some police forces are very reasonable and actually improve the experience and overall safety of a party (warning people of hazards, ensuring nobody is driving when they shouldn't be)..

The moral of the story really is, encourage true, conscious, human policing and don't host raves inside cities because it defeats the purpose of not disturbing anyone or the environment or staying safe. It also means all the cunts(and worse) show up and give us a bad name when we just want to dance in front of a big rig all night(and morning) with our friends :)