For my first birth two weeks ago, it was all natural because:

Read 'New Active Birth' a few times....
Read all the 'Labour and Birth' threads many times over....and all of the 'Birth Stories' on BB.
Only thought of labour in positive/encouraging terms.
Stayed at home, in the bath for as long as I could (turned out to be until 10cm!!).
Made sure the midwife I got read my birth preferences.
Breathed long and hard (spat/spittled all over midwife!) during later contractions.
My membranes had to be ruptured as I was 10cm for ages.....and it killed to try to push with them all full.....the darn things refused to break on their own.
Prayed a whole lot during the pregnancy (very specifically for all sorts of things).....and I really believe it was God who got me though it so well (really!).
Labour lasted from 4am till 11:54pm same day - but it was all manageable.

Good luck!!!