Hilton HHonors - What links do you follow for booking?

I wanted to know throught what links do you follow to maximise the most points. Right now I am going through the Northwest Link (http://www.nwa.com/offers/milesafari/) and getting the 5 points along with the 500 points for booking online with my amex. I have around 20 more stays comming up and figured thats an extra 3000 points just for following the link.

Use of the link is NOT required to get Mile Safari points.

How do they know that you stayed at the hotel, is it through the double dipping? Right now I have hhonor and hhonor points for my double dip.