I managed to negotiate a bit with my hotel a couple of years back, probably because I was gettign hitched in January!
I negotiated 25% off the cost of the house wines, i was a member of the gym at this hotel and they do offer 10% when you eat / drink there so I asked if they would offer a discount as a long term customer, and they did. The also let me pick and choose off the menus, ie instead of the 5 menus on offer I choose starters from one menu, main courses from another, and they charged me the lower per head cost.
Also ask people like the car hire, suit hire for a discount, I brass-necked it and got 10-15% off most of them.
And my personal cost cutting recommendation is forget about 'favours', I consider them money wasters! Put that money into some chocolates / biscuits for the coffee / tea / sandwiches in the evening, that is one of the things people still talk to me about (and that the servers came out with seconds after the main course).