This is one that you absolutely need a grill basket for but I don’t think it’s necessary to do anything to them before you toss them on the grill.
Approximate quantities: 1 pint of cherry tomatoes; 1 tablespoon olive oil; salt and pepper
Grill the tomatoes in a grill basket at a at a medium high-heat for about 6 minutes, turning, or gently shaking the basket so that they can roll, about halfway through
After about 6 minutes, they’ll begin to char and blister, take them off and then drizzle them with olive oil, salt, and pepper
The slightly trickier part is getting to know your grill and it’s temperatures. I’ve provided a heat and time range for everything that should work for almost all grills.
Almost everything needs to be turned, or if it’s in a grill basket a good shake at the halfway point will work, so what I’d recommend is plan to check it and turn it halfway through the shorter time range that I suggest, and then, to check it again for doneness, at the end of the shorter time range. This way, if you grill doesn’t run as hot, and you can see that you need more time, it’s easy to leave the second side on for a few more minutes.