I think that protesters need to be given clearer guidance as to which areas are allowed and which ones are not. Hopefully this would allow large numbers to protest peacefully, and to be aware that they will be moved if they deviate from these areas.

I don't know why water cannons are not used. They are used from a distance and are effective with far less damage than a line of officers going toe to toe with protesters / rioters. Similarly, horse charges are intimidating and generally work very fast with little damage except to the shorts of those caught off guard. Even tear gas is unlikely to cause the damage that seems to be doled out on occasion (although those with asthma had better keep well away from prohibited areas).
Tazers probably wouldn't work on the numbers required and is probably rather OTT in most cases. A lower power electric charge transmitted through the air via a laser mediated ion stream might be useful; I think the USA was working on a laser that was strong enough to cause discomfort rather than damage that would be another method.

And I think that those who carry home made shields / gas masks / weapons should be detained as clearly they're not there for a peaceful protest.