First iPhone, what should I Do?
1) That entirely depends on what you want to do. There are a bunch of app recommendation discussions here based around games, productivity, etc. Rather than rehash them, I'd suggest searching those out.

2) Plug it into a USB port on your computer. The phone also comes with a wall adapter for the USB cable so you can charge it from a wall socket.

3) Don't stick it in the oven or the freezer and you should be fine.