Get the grill very hot with the highest heat setting possible. If you’re using a charcoal grill, they’re ready as soon as the coals are covered in white ash.
Mix together the salt, garlic powder, onion powder, black pepper, chili powder, sugar, cayenne pepper and allspice in a small bowl.
If the shrimp still have their shells on, remove them, leaving a small bit at the tail.
Remove the black vein running down the back of the shrimp.
Run a skewer through the middle of the shrimp (not lengthwise).
Continue to do this with each shrimp until you have 6 on each skewer. The shrimp should be nestled together with each other.