For crackling, should I give pork a blast of super heat at the start or end of roasting?

The heat should be applied at the end, if you covered the crackling with tinfoil and slow cook it will soften (not crispen!) due to the steam and the trapped fat.

For the best crackling, score the top before you cook it and pour boiling water over the top. Sprinkle it with salt, then cover it with tin foil to cook it, removing the tin foil for ten minutes at the end. Makes fantastic crackling every time!

This is the way I've always done it...

I like to give the shoulder a good blast at a high temperature at the beginining to get some good colour and add flavour. Score the skin, season with salt and give it about half an hour at 220 degrees C or higher, uncovered, with some stock veg in the tray. Take it out, add some herbs or flavourings if you like (bay leaves, lemon, thyme, spices etc) pour in half a bottle of wine and about the same in water. Cover the shoulder in a sheet of baking paper, then cover tightly with foil (occasionally foil will stick to the fat on the pork, so it's best to have a layer of parchment between).

After it's slow cooked at the low temp and is falling apart tender, take it out and turn up the oven again. Strain off all the juices for making your sauce, then carefully remove the skin and lay it on a seperate, dry, tray and give it a blast in the hot oven .

This has always worked for me as you're getting perfect meat and perfect crackling. Slow cooking meat always makes the skin flabby and if it's a joint as large as a shoulder I'd prefer to remove the skin and blast it at the end on it's own rather than still on the joint as you run the risk of drying some of the meat in the process of drying the skin enough for it to crackle.

Hmm... crackling....

in my opinion the whole idea of crackling is to remove the water so score the skin the previous night rub a good load of salt in next day pat dry and blast for 20 mins at 220 then reduce to 160 for the durataion until you can fork it and the juice is clear i also salt, pepper garlic and cumin my roast(whole cumin), elevated is better so on a rack or on abed of veg to stop it stewing.

Always make sure that the rind is dry and then scored. I then rub salt onto and in between scored rind followed by a little olive oil and then Schwartz pork seasoning. I then put it into the oven at 180 uncovered and have never failed to get the perfect crackling. With all those tasty herbs I would rather eat the crackling and forget the rest!

Don't forget about your trusty broiler. I like to do this instead of cranking up the oven since it generally takes a lot less time to reach an ideal temp and it doesn't heat up my kitchen nearly as much (which may not be a problem for you) and it's a concentrated heat source so your not going to be heating the entire piece of meat (relatively speaking, i know the oven will also get hotter over time).

I echo the sentiments of scoring the skin. You could also consider a shallow fry on the skin side only to achieve true cracklin' texture.

This may sound strange, but once I’ve scored the rind and rubbed in the salt and then let the salt draw out the moisture, i dry the rind and rub off the salt and then... here’s the strange bit, I blast the rind with a hair dryer on full power and full heat until it noticeably begins to dry and tighten up. This mean I’m taking less moisture into the oven with the joint. I put the joint in at 220 for 30 mins and then turn down to a good temp depending on how long I am roasting for and the size of the joint. I don’t roast on fan either as I’m sure this tends to move moist air around the oven. So far I have had my best results with this methid