It's all random and based on time of entry. As far as the click here option, I always play the game the first time, just to see if it is fun. If it is not something that interests me, I will, from that point click the click here button. I have won several times using it.
As far as the where did you hear it from question, I don't think it matters. Sometimes I click friend, other times I click sweeps site. If they ask for a sweeps site name, I always put SA because they may list the sweep here in the future and provide SA with some referral income.
That's just my 2 cents.