In reply to glaramara:
Do you have a guidebook ? As far as I remember the descent is down a really well worn path to the left of the coastguard station (looking out). The pinnacle itself is very obvious once you head down there. As said above, you can use most descents at low tide, though.
I'm not sure what the start of terriers tooth is these days after the rock fall, but I suspect you'll need fairly low tide.