By asking Hilton customer services you can usually fast track to Gold with 4 stays in a 90day period. They tell you that you have to phone back and have the stays registered but it seemed to be applied automatically when I reached my four stays in June.

Depending on your CC preferences, I also got a letter about their VISA card last week, card gives you silver status (been this way for ages) and 10K spend per annum gives you HHonors Gold (new).