Find out when high tide is, and don't go exploring for secluded beaches and inlets when the tide is on its way in. Much of the shoreline is rocky cliffs, and you could get cut off by the rising tide.
Destination Cornwall offers some useful resources.
So I had waited near on a quarter of a century to see the ruins of Tintagel; but if you are disabled in any way and it affects your walking, you can totally forget about seeing the ruins of Tintagel castle. There are hudreds, if not thousands, of very steep steps to get to the ruins. I could have cried, there was no way that I could ever manage these steps and there was no other way to get to see the ruins, so I had to send Chris, my sister and her husband on their own to see it and get the photographs.
You should be very careful walking around the top of the Island, as there are no barriers around the cliff edge, and few warning signs either. It can be very windy, and if it's misty you might not be able to see exactly where the edge is. Children and animals should obviously be kept hold of here.
Although personally I wasn't too tired after I had climbed the steps all the way down and then up again, lots of people struggled. Going down was quite hard in my opinion, but more in the way that you have to be especially careful, for one misstep could have you landing all the way at the bottom, breaking perhaps some bones and what else along the way. Going up you can see where you have to put you feet next, but is more stressful for your body. Make sure to bring some water in case you get thirsty, or when it's hot. You cannot buy ater at the top of the rock where the ruins are situated, so keep that in mind.
The stairs all over this place are steep and a little dangerous - i wouldn't want my elderly parents walking them - even though the truck will take them up and down the very steep hill to the entrace to the castle - once they pay their entry fee - there is not much more than step after step!
Here is a picture of about half the stairs that had to be conquered in order to get over to see Tintagel... You have to go down these stairs and then up about as many on the other side in order to get to the site. So just make sure you're up for it, if you go! I was a bit sore for the next 3 days, but Tintagel was so awesome, it was more than worth it :)