Contractions

I know this may seem like a dumb question but to a first time mom who has no idea about this kind of stuff it is important.

I am getting farther along and have been experiencing some light Braxton Hicks occasionally. However, I was never taught / told about how to properly time contractions. I know to keep track of when they first start however I have no idea how to know whenever they end. Is it whenever the pain stops and my stomach goes back to normal?