Keep to the planned route
DO NOT follow other people like sheep - you are an intelligent student. If you start walking over broken-down barriers, it should give you an inkling that you're going in the wrong direction. Turn around and ask a policeman where you're supposed to be.
Parliament Square was not the planned route of #dayx3 and after continuous violence against the police and property, the Square became a crime scene.
Whenever this happens, you cease being a protester and become either a witness or perpetrator and are part of an official crime investigation. Think of it as CSI London.
From here on in, you will find you're not in Kansas anymore. Don't bother complaining as you should have been somewhere else.
Don't get involved
If you see a gang of people wearing hoodies and balaclavas starting to rush towards a police line or smashing their way into a building, DO NOT follow them to see what's up and then complain when you get hit by a police baton.
Getting cool photos to upload to your Facebook page is a really silly reason to be anywhere near trouble - even if you have got a new mobile you want to show off.
The police will have restricted vision because they're covered in paint; have had continuous verbal abuse thrown at them; along with sharpened posts (which are better known as spears), steel cages, concrete blocks and snooker balls. They will not be happy-chappies. Keep away from them.
Similarly, if you see a line of police horses, they are not out on a hack - they are there to scare the bejesus out of you. If a thin line of police are being attacked by thugs, they will charge only as a last resort to protect the line.
You may not see the reason for the charge, but there will be one - and they don't tend to give out warnings. So if you find yourself nose to nosebag with a police horse, you are in the wrong place - move to the edge of the crowd and find somewhere else to sit it out.
Bring your Common Sense
If someone is injured, accompany or carry them towards a police line (that isn't being attacked at the time) and ask for medical help. DO NOT ring 999 because you're missing your last train home (or someone nicked your snowman).
Follow
@CO11MetPolice on Twitter so you don't miss any instructions. They will tell you where they will set up toilet and water facilities if the containment will be in force for some time.
There is no excuse for urinating against statues of figures that fought to protect your right to protest. Your face - or builder's bum - will be in all the next day's papers and you will be arrested because your ex-girlfriend/boyfriend will shop you in (if you've ever had a partner that is).
Be prepared for the long haul
Boredom, being chilly or becoming peckish are not excuses for leaving a containment. You're the one that didn't follow the planned route, so you're not going anywhere now. It was your choice. Stop whingeing.
The police are not information desks and are only doing what they're ordered to do. You'll probably know more about what's happening than them because they tend not to check their email while they're avoiding a barrage of missiles.
They won't think about letting you go until the children have stopped their tantrums, so keep warm but don't start burning national monuments or other people's property to do so - burn your own banners. Hopefully, you were sensible enough to bring warm clothing and gloves. I would advise against bringing a balaclava unless you want to be targeted by a police baton.
Containment is a way for the police to get all of you into a single, secure area. It is likely that if you are contained, it means that there is either trouble elsewhere that requires more immediate attention, or that a slow release is being planned. This is for your own benefit, to weed out the thugs, so they don't end up on your next protest. Be patient - it will takes hours and hours and hours... and you will miss your last train. Sorry about that.
While you're waiting, keep in mind that everyone who kept to the planned route is now watching you freeze your proverbials off from the comfort of their sofa with a steaming Pot Noodle, so it's probably best not to be there in the first place, eh?