If you reward a tantrum, you will condition your child just like one of Pavlov's dogs. Every time your toddler wants something, she'll throw a little fit. So don't buy your child the candy she wanted just because she makes a little scene —or even a huge brouhaha. Instead, try to demonstrate that the tantrum has no effect on you whatsoever. It will not change your mind one little bit.
The reasoning behind this rule is simple: tantrums should be treated like speed bumps. You may slow down and ease over them for a second, but then you get right back up to speed. They have absolutely no lasting power over you.
Besides, if your child is out of control, then he's out of control. Is this really a punishable offense? Probably not. The tantrum itself is probably frightening and punishing enough to your child without having you add further punishment to it.