Riot Duty - Class 101
Here is something for local North American law enforcement agencies can learn from their UK/ Europe counterparts (esp. UK)

Parameter outlining
While it's great to have a large parameter cordon (a rather silly self-comforting idea really), it requires alot of manpower and equipment to cover all possible points of entry into the parameter. Rather, keep the parameter cordon size as small as strategically possible (between 300 - 700 meters). If the idea is to keep long range projectiles out of range, you'd need a very big parameter area.

Essential Equipment
Forget about mace or pepper spray. This requires close range work, which can become dangerous if the law enforcement officers are not specially trained for riot duty. Instead, utilize fire engines with high pressure pumps or riot vehicles with high pressure water cannons. The pressure from those cannons are strong enough to push a large crowd away without hurting or killing anyone. Also, this is very effective on cold days as it would literally freeze rioters/ protesters. Truncheons and rattan/ plexiglass full-length riot shields are essential for riot duty. Always have gas masks and grenade launchers available as well. There's nothing like CS/ tear gas to scatter an angry mob, but remember not to use the water cannons in the same area as where the tear gas grenades are deployed. Riot horses are great for crowd control as well, it is the intimidation factor that causes most people to move away from those big horses. APCs are much more effective and harder to flip over than patrol cars.

What To Do?
Concrete walls are far more effective than metal fence/gates, and they are heavier to move or push down. They also provide cover for police officers against projectiles thrown by the mob. Never use patrol cars as barricades. They are easy to flip over and it is hard to redeploy cars than are used for barricade duty since they park so close to one another. Instead of having a single long line, deploy the Box maneuver. This maneuver is much sturdier than a single line since there is no back up should one or two officers fall. The Box has at least 5 ranks and if an officer should fall, he/ she is easily recovered and replace by another officer. The shields also protect them and grenades are launched from the inside of the Box. Riot horses are used to herd and corral protesters/ rioters to a containment area. As well, have sniper teams on surrounding rooftops to deal with any potentially armed protesters. FAST (Fast Action Strategic and Tactical) teams are deployed to deal with any possible terrorist threats. Once again deployed on rooftops, on the ground and in helicopters.

While I'm all for a peaceful protest, hooligans and any protest that get out of hand must be dealt with swiftly and efficiently to minimize collateral damage to nearby properties. But by no means does this mean using lethal force, unless it deals with terrorists.

well, enough of digress from work
back to work I go!
*sigh*