How did you know you were going into labor?

Just curious! 39 weeks and I swore something was going on because I was contracting every 6-4 minutes from 8am till I got to the hospital at 9pm and was having terrible cramps and lightening crotch along with it; of course everyone had me convinced I was in labor and told me to go to the hospital ASAP; mind you it's such a hassle because my hospital is 45 minutes away... Anyways as soon as I got to the hospital they stopped and I was sent home 20 minutes later. I guess they were just Braxton hicks.. They were so consistent though? I'm currently 39w2d now and been 1cm and 50% effaced since 38 weeks :(
So I'm wondering how did you know you were going into labor? What made you realize shoot, it's time?! I'm a FTM too so I'm new to this!