Barbecuing shouldn't present any additional food hygiene problems. A rare steak is rare whether you grill it indoors or out. Chicken should be cooked through, just like you always would. Take the same precautions when preparing food, just as you would in the kitchen. Then preheat your barbecue for 20 minutes or so. This will kill any nasties on the grill itself, and make sure you are cooking at a consistent temperature.