Hi Sky,
I've always started from the Cow n' Calf on my visits to the Twelve Apostles. Brief directions...
From Car Park head up the side of the C+C, in front of you is a high ridge (you can see the Pancake Stone to your left). Clamber up there and you will find the Haystack and Planets cup n' ring marked rocks. Follow the path to your right, which takes you to the reconstructed enclosure at Backstone Beck (look out for more C+R rocks on the way). Follow the path past the enclosure and turn right at the top of the ridge. Keep on this path until you reach the main x-moor path, part of which is boarded over. Keep on ahead to the ridge in front of you, at the top of which you will find the Lanshaw Lad boundary stone. Take the path that bears left and after about 100 yards, you'll find yourself right on top of the Twelve Apostles.
The lazy bugger's way is to drive up the Ilkley Road and park up at Whetstone Gate by the radio transmitters and take the path past the Thimble Stones, over the moor top at Nixon's Station and straight forward to the Twelve Apostles.
Happy Huntin'!