So how do you spot this behavior going on? 
You need to watch the order book very closely.
I'm interested in the following:
When and under what circumstances does selling induce a sell-off? What is the difference to regular market sells? How does it turn the sentiment around?
Would you say seeing many arbitrary small bids to buy and sell is a sign of manipulation. e.g. on ActM seeing many bids for <100 shares?