Between 1st April – 30th June 2013, Hilton have an ongoing promotion with Miles and More awarding 2000 miles per Friday, Saturday or Sunday night stay instead of the usual 500. Here's the registration link which also includes the full terms and conditions.
You must have your HHonors points earning preference set as “points and fixed miles” before you check out. Hilton have a reputation of not reversing transactions once points from a stay have been posted into an account — even when you've done everything correctly, so to be safe make sure you set it before you even check in!
To really maximise this opportunity, you can also register for their Q2 promotion of 2013 which also awards 2000 HHonors points per weekend night. Note that for this second promotion a “weekend night” in the Middle East or Africa is classified as a Thursday, Friday or Saturday night stay, thus tightening the double dip opportunity a little.
Not too bad if you're a perennial Miles and More collector though!