In my NCT group of 7 two had labours which weren't particularly painful, one a home birth, one induced with the pessary in hospital, had a lovely waterbirth.
I was booked for a home birth but it went so quickly (nearly 6 hours start to finish) and the midwife was at another birth so once I started feeling the 'downward' motion got a swift taxi to the hospital.
The pain amped up quite quickly in my case because things were moving fast but it wasn't horrendous in any way - it hurt yes, but what would happen was I would feel my muscles tensing, like electricity 'gathering' in them, and then it would build like a wave building height up to the peak, say three breaths, and then down the other side, and a 2 or 3 minute break.
When I was fully dilated it stopped hurting, and it was just a feeling of power and pressure - like a very magnified version of when you're going for a poo. Now having said that, me and my two friends above had labours where the baby was in a good position for birth, not particularly large etc. You can encourage a baby to be in a good position by using the positions suggested on the spinning babies website during pregnancy, but ultimately you can't control a baby being say, back to back, which is a position which can hurt more than is typical.
The absolute best thing you can do is the positive birth company digital pack - it is absolutely amazing at explaining the whole process of labour, your pain relief choices and how they work, and it has a great birth preferences template. It's only £35, and 100% worth it.