Just wrote a huge post, then deleted it as too much waffling 
But basically it came down to 2 important things for me being to listen to the woman, and not to automatically dismiss what she is saying because of thinking they "know better".
In particular, not to dismiss what the woman says about how much pain she is in/how far along she thinks she is, based purely on a phone conversation or a single examination and on some textbook idea of how labour goes.
Both I and one of my friends had problems with mws (not sure if it was the same one both times!) not wanting to "let" us come in to hospital when we phoned, as they insisted it was still too early, we didn't need to be in etc... - in her case, by the time she insisted on going in anyway she was 8cm dilated, in my case 6cm, I had been having contractions for nearly 24 hours already, and we found later that baby was stuck in an odd position so I wasn't dilating properly. If I had waited for contractions to be as frequent as she said, I would NEVER have gone in, and would have had to continue coping with a lot of pain on my own (and DS would have stayed stuck!). So it would have been better if she could have taken my word for how I was feeling, how much stronger the contractions were getting etc and let me come in earlier.
The other time, I was nearly sent home as at assessment they said I was only 2cms dilated - even though I said cxs were getting really strong and really frequent. Luckily (and only because I was hoping for VBAC) they eventually arranged for me to stay on in an antenatal ward instead - and within an hour I was nearly fully dilated and getting urges to push! So it would have been good for someone to have taken it seriously when I said things seemed to be moving really fast, and not almost sent me home.
Saying that all the other mws we dealt with were very good, and some were absolute stars!