Don't start with, "You people..." ever. That's a hourly wage slave in a cube on the other end of the line who probably can't afford what you're complaining about. They probably have no control over policy.
Don't follow it up with, "...are trying to screw me!" No, they're not. They are the very people who are empowered to help you. Try to remember that you want them to want to help you.
"How would you like it if I took my business to your competitor!?" So they can get THIS call? OK! Works for me.
Try not to complain about something ridiculous they have no control over. Like rain in a subtropical climate. Especially when this person is well aware that there are indoor entertainment options for just this circumstance. Make sure you have a legitimate beef. AND, if you're nice about it? They may compensate you even if you don't. They won't want to if you're a jerk.
Don't tell them blatant untruths. They have records of prior complaints (YOU have half a dozen!?) and of equipment failures (that attraction was not down that day) that they can double check if your veracity is in question. Computers are a wonderful thing.
In short? It's nice to be nice to the nice.