We need some advice-

I was just wondering if there is anyone who might be able to help with some advice. We're going to NYC this summer and I want to make the most out of our time there but I'm not sure the cheapest way to go about it. For example, we want to go to a show but I don't know if it's better to purchace the tickets this early in advance or to just wait and see if we can get discounted tickets there. We'd also like to some really good restaurants. Any advice? It would be really appreciated.