The babies will instinctively crawl down the glass into the water, from there if you have fish that won't go after them you could have quite a few in your tank. I had two egg sacs hatch before and it was quite exciting seeing them go straight to the water.
If you do get eggs laid above your water line do not soak them or submersed em in water. If your tank is humid enough that will suffice to keep them going. I know some people must them with a spray bottle. Also after 2 weeks or so shine a flashlight into them and if you see black dots you have babies. If they are clear they were fertilized.