The trick to cooking asparagus on the grill is to skewer it. Of you use two skewers through the spears to make a raft of asparagus, it's easier to turn the asparagus on the grill. It also makes it a lot easier to season the spears, since they're all right next to each other.
Garlic salt, to taste (or garlic powder and salt)
Pepper, to taste
1 teaspoon parmesan cheese powder (or 1 tablespoon finely shredded cheese)
Thread the asparagus onto the skewers as shown in the photo. Drizzle with olive oil, then sprinkle with garlic salt, pepper, and parmesan cheese powder or grated cheese. The olive oil with help seasonings stick to the asparagus.
Grill the spears until they're warmed through and you've got some grill marks on both sides. Remove them from the skewers to serve.