You get a show when your cervix starts to dilate/efface (open and get shorter, softer, thinner) but as someone said just now, sometimes you don't see it til you're in very established labour, and sometimes you can see a show a week before you have the baby. Mine was like a great big lump of rubber glue with blood streaks in it, first baby. I've heard it can come out as lots of thinner pink discharge though. It's a good sign whichever form it takes!
Try not to focus on labour hurting too much, it does but you'll cope. Just remember that when you start to think "this will go on forever" you're often right near at the end and almost ready to push. Same with the pain, it doesnt keep getting worse forever, it will reach a peak before pushing and then change.
Ask your midwife to let you know if they think you're near the end or in transition (the bit where the contractions are most intense, before pushing, where you might feel out of control or panicky) and to remind you that your baby will come soon. No-one ever told me those things so with my first baby I sort of got lost in panic worrying about worse and worse pain, whereas if they'd said "you're nearly there, this is as bad as its going to get, few more contractions and you'll be ready to push" I'd have coped better!
Each contraction is one closer to meeting the baby. You only have to cope with that one at a time. Breathe deeply through it, use your gas and air if it works for you (nice deep breaths of it at the start of a contraction as it takes a few seconds to kick in each time) try to keep your face and mouth soft and loose rather than gritting your teeth (apparently it stops the muscles down below clenching up too) and try to stay off your back as it makes labour more painful, makes the pelvic outlet narrower and means you push the baby uphill instead of letting gravity help. Having your partner apply strong counter pressure to your lower back during contractions as you lean over the bed can be really helpful. As can just leaning onto them and feeling loved and supported, don't underestimate the pain relieving qualities of that!
Best of luck everyone, I'll be eating my words and begging for pethidine in a few days, you watch. 