Rough chop the onion (about ½ cup), take the skin off of about ¼ cup of garlic (about 6-8 cloves, or 2 oz if you want to measure) and toss it into a food processor and pulse. Do not over pulse or the onion will get too wet, which will cause you to have a wet meatball. Next, scrape out the onion, remove the leaves from the parsley and basil and toss them into a food processor and pulse. If you don't have a food processor just finely chop it all with a knife.
After everything is finely chopped toss it into a big bowl with the rest of the ingredients. The key with any meatball recipe is to very carefully and lightly mix everything together. It's almost like a light toss rather than a rough mix. If the mix is too wet add some extra bread crumbs. Don't pack everything together really hard of you'll have dense meatballs. You want them to be light and fluffy. If the mix seems too wet add some more bread crumbs.
Once everything is mixed together lightly form meatballs in your hand. The size is really up to you but remember that bigger meatballs take longer to cook.
Once the meatballs are made they can be stored in the fridge for as long as you like (within reason) until it's time to prepare the grill. You want to cook them throughout but you don't want to burn the outsides. I prefer a medium heat spread out all over about ¾ of the grill. This works out to be about ¾ of a charcoal chimney lit and dumped out evenly around the grill. Don't have a high temperature or you'll have meatballs with a rare inside and crisp outside. Not good! Since the meatballs are fragile I take some oil, wet a paper towel, and rub the grates to clean them and to help things not stick. I've had zero problems with meatballs sticking to the grates but this is an extra safety measure. You are also more likely to stick if you have a wet meatball (see note about extra bread crumbs above). When the fire is ready grill the meatballs for about 10-15 min. Don't be afraid to check after 8 min.