hb, i love grilled squid!
i've found the same problems with grilling them, so here's a few tips.
first of all, after cleaning the body cavity, try to remove the purple-ish skin. then slice into 1 " thick rings, and skewer them so they sort of look like a line of figure 8's.
if you leave the body whole, and the skin on, it is a little trickier to get them cooked just right. the outside cooks but the inside stays a little too raw. but if you cook until it's not raw inside, they become overdone and tough in the blink of an eye.
grill the skewers over as high heat as you can manage. if done well, the edges with just char a tiny bit as they finish cooking through, just a minute on each side.
my favourite way of eating them grilled is thai style. serve over a bed of lettuce and shredded carrots, and top with lots of fresh cilantro and sweet chilli sauce.
another good way is in a simple italian salad. mince raw garlic, celery, red onion, and add to evoo and red wine vinegar with a pinch of oregano and parsley, and s&p. toss the grilled squid in the dressing, place over a bed of arrugula, and top with diced fresh tomatoes, and a little more fresh parsley. drizzle remaining dressing over everything.
god i'm hungry for squid!