What you have to do - Upon registration, you just have to install their adbar. After that, you just login and you're good to go.
How it works - The adbar you just installed floats on your desktop. You can drag it wherever you want ot just put it in a corner and forget about it. It is not a huge, pixelated bar, so you won't notice it at all most of the time. What is more, if you watch movies or play games it doesn't even show up anymore, even if you're still earning money from it, which is great. It has a refresh rate of 15 seconds. After that, the advertisement banner will change and so on.
Pay rate - For every displayed advertisement you receive a certain amount of points, depending on your account status. There 6 types of accounts right now: non-VIP and VIP 1 to VIP 5. The higher your VIP level is, the more you will earn from each advertisement. Right from the beginning, you're given a VIP1 status, which is pretty nice, because you earn 1.25 points from each ad. The payrate at this moment is of about 1 euro (not dollar) for every 11.000 points. It may not sound as very much, but given that you don't do anything I think that it is worth the time.
Payout - The minimum payout is 15 euros for virtual accounts (Paypal and Hipay) and 20 euros for physical checks (for France only). Here is the officialforum thread for payment proofs.
Referral system - The referral system is great for a passive earner. You earn 20% of your level 1 (direct) referrals' earnings and 5% from your level 2 referrals. This includes points from ads, clicks, lottery and bonuses, without any restrictions.
What's more, if you don't have enough time to seek referrals or just want to take some chances, you can participate in the referral lottery. The concept is pretty straight-forward - you buy tickets; each ticket is another chance. Please note that they are not referred to you for a certain amount of time - you get them for life, if you win of course.
Note: You DON'T have to click on ads in order to earn from them. The only time you may want to click on ads is when the bonus banner is shown.