1) Opt for lean meats, and make sure you remove skin and excess fat beforehand.
2) Don't grill for too long. If you pre-cook meats in the microwave and cut them up into smaller pieces, you'll shorten the time it takes to grill. This means that carcinogenic chemicals that come from charring will be less likely to form.
3) Marinate with stuff like lemon and vinegar-based marinades for a healthier option.