I had period like pain at irregular intervals on and off for days before I went into labour. When the period like pain started to come at regular intervals I knew something was happening.
For me the majority of my labour was just like having period cramps on steroids. They started (and stayed) mild from about 4am on a Monday morning and then ramped up about 9pm that evening. I lost my mucus plug at about 11:30pm and finally decided to go to hospital - my waters never broke, the midwives had to do that at some point during the last couple of hours. Our little man was born 4am on the Tuesday morning