Here's my standard list of items I always bring:
Briar pants:
Lightweight boots for warm weather +0F:
Jacket:
or vest:
Gloves:
warm:
cold:
Any blaze orange hat
Any blaze orange beenie
First aid kit, with tweezers and antiseptic!
A couple things to remember...know your terrain and weather. Last couple years on opening day it's been hot. So pants and a tshirt, with a vest.
Always wear eye protection, it's saved my bacon a few times and the other guys I hunt with. Assume you will get peppered, and realize that blockers/walkers don't always have control of their shot patterns. Pellets do collide and go off course. I always wear layers. Underarmor is my preferred gear. I've worn it since 97 under my football gear and swear by it.
Last but not least, SOCKS!!! Get a good pair of socks, your feet will thank you for it.
I wear a shotgun ammo belt for hot days (+15F) for faster reloads. A lot also depends on the dog situation. If I have my dog with me, I wear my dog vest.