I've been there twice, its built up so much since going there the first time. I stay in Canada when I go.
If you take the Bridge Walk across the river be sure to bring your passport!! They do not tell you this when you pay and enter the bridge, only when you try to get back off! We got stuck on the bridge for awhile until the customs guard finally let us through. The only reason we were able to come back into the country was because he remembered us. I dont know if he kept us there for humor or for what but we started to panic because our luggage, car, passports, and everything was at our hotel! We couldnt get back into the US, or Canada....we were stuck! It was pretty late out, and we were a group of family so I guess he understood. I guess there is one small sign posted before you enter the bridge but the words are about THIS BIG!!
You must go on the Maid of the Mist! I went on this both times, and it was awesome! The boat drives really close to the Falls, and its pretty exciting! Dont worry they give you cool blue panchos to keep so you dont get AS wet!
Dont forget to visit the garden right next to the falls, its pretty and very romantic! While you are there look on the small bridge closest to the street and tell me if "HC + VG forever" is still carved there. My ex did it lol. Scratch it off! We were soooo not forever!