After scoring, scald the pork rind with a kettle of boiling water. Leave to dry for a couple of hours (or if time pressed, pat dry with kitchen towels and give it a blast of the hair dryer) then rub in plenty of salt and oil just before putting into the oven.
Put it in the hottest your oven will go until the rind starts to bubble, then turn down to moderate. Keep a close eye on the bubbling stage, it can burn pretty quickly if you get distracted for a moment.
ETA: I don't remove the crackling, but carve it with the meat. For that reason, I score straight across and not diagonally. I can't see who posted this, but the recommendation to use shoulder is spot on. A shoulder or belly are my preferred joints for roasting. Like duck, tasty roast pork needs plenty of fat to flavour the meat.