when the sentence means directly or indirectly that someone gives something to someone, you use 给. For example,
1. 给他打个电话。 Call him --- the result is that somebody "give" him a call.
2. 妈妈给我织了件毛衣。Mom weaved a sweater for me --- the result is that mom will give that sweater to me.
3. 再给我来一碗汤。One more bowl of soup, please --- the result is to "give" me one more bowl of soup.
when sentence has some influence on the object, you use 对. For example:
1. 喝酒对身体不好。---drinking has bad influence on health.
2. 他对你不好。--- He treats you badly and the result will influence you physically or mentally,
3. 我对实验结果很满意。--- I'm satisfied with the result of the experiment. And the good result of experiment is supposed to benefit you, right?