Lee,
I was there last year and it was hot!! Take water and sunscreen, plus a hat or visor. Go early and walk around before taking your seat...various tennis vendors are there selling their items. Also, kiosks are scattered around selling US Open Tshirts and hats. I always like to take a shirt back home to wear.

Another thing you might want to consider, buying your lunch from a deli in NYC and taking it with you. I was on a "women's retreat" as in girlfriends met in NYC for tennis and shopping. The more frugal of our group bought their lunch and took it in to the US Open. Others, me included, were too lazy and bought our lunches at the site, more expensive, food was fine.

Also, different entertainment groups perform in the plaza areas. Lots of fun to watch. Although I like viewing the tennis, it's the people watching that I really love.

I'm sure others here have much more experience with the US Open. I hope they post and give you some real "insider" tips.

Have fun!