When I had cable I used to call and "ask for the promotions" and they would give you a discount, if that didn't work I would say I want to "switch to X company and to shut mine off" and they would quickly offer me a promotion to stay w/them. I think they caught on, probably put it in the notes about me, so last time I threatened to cut it they called my bluff. We've been w/o cable for the last 4 years and I'm very happy. We do internet ($60/month) and Netflix + Hulu. What I found with cable is that it's the same stuff on Hulu but there is so much more crap on cable that I never wanted/needed. If I'm on vacation or at my parents place and they have cable, I can never find anything good on.
They also jacked up my internet bill 2 years ago, and I called and said "the increase was hard on our family and if they could do anything", which at the time it really was as we had 3 kids in daycare, so they gave me a 2 year promotion at increased speeds for only $55/month. After that ran up it went up $10, and I called again, they dropped it down to $60. If you want to keep your cable in check, you gotta get rid of the stuff you don't need. I need internet b/c DW and myself both work from home, and Netflix/Hulu is great, and the total is $16/month for both.