Adjective or adverb?

Whenever I have to speak or write English, I am confused with usage of adverbs and adjectves so many times. For example, 1. I am going to throw a suprise party for her. In this, I think that "for her" can modify the noun "a surprise party" as an adjective phrase and also can modify the verb "throw" as an adverb phrase without any meaning difference, right? 2. I had a meeting to discuss the issue last night. In this, "to discuss the issue" can modify both the verb "had" and the noun " a meeting" without any meaning difference, right?Please tell me the way I am thinking is right or not and there is more I should know about this grammar.As usual, thanks a lot for great help in advance.