It's not always about big premiums. Small orders can be leading indicators that big orders will be pouring in soon.
Big flows almost always start with a small order, so pay close attention to the small orders, particularly “unusual” ones. Why?
Institutions don't just take significant positions immediately. They build positions slowly over time by averaging up into winners and cutting losers early.
So, you may see small flows at first as they start to build a new position. As they become more confident in the position (and begin to see some returns), they start placing large orders.