Everything is on sale, especially in the current economic climate, usually just for the asking. A smile, warm demeanor, and genuine gratitude go a very long way, as you seem to have already experienced.
I always followup a discount or good service with a reciprocal treat (although watch out: in some areas/cultures, this could be insulting). In hotels/motels that I have stayed, following up has often resulted in yet another perk: champagne compliments of the manager, discounted/free additional stay, special treatment at a local restaurant, et al.
At the same time, I think there is a time and place for haggling. I have been offered discounts when I did not think it appropriate or that I should pay the full price. It's a matter of context and I think it's one of those important social skills.