Although I agree with Crow in that proper grilling should entail charcoal (preferably placed in an oil drum that's been split open lengthways to provide more space for food to be grilled), I do welcome you to the ranks of barbeque chefs.

As for spices and/or marinades, I tend to like having the wet marinades and then use the marinade as an additional barbeque baste during the coking process. You should definitely try to whisk something together yourself for next time you are in charge of the grill (like any proper man should be ).