But...I've never hiked a day in my life. anyway, I'm excited though. It's not backpacking, just a day hike. so what should I bring?

plenty of water

Water
hat
jacket if there's any chance the weather could turn or if you'll be gaining significant elevation
a snack if you'll be out for more than a few hours
camera
cell phone in case you have a problem and need to call for help

What theox said except I always bring a snack just in case of emergencies (if you get lost, you'd be super happy that you'd packed a couple of granola bars or some trail mix!).

And I don't know where you live, but I've often been hiking in bear or cougar country, so packed a whistle... not only for scaring away possible wildlife, but also as an emergency signal.

Just want to say have fun!! I love hiking!!!

I'll definitely let you all know how it goes :33