What exercises can you do at home to help get abs and pecs?

Crunches will always be best for abs. Use a little weight, holding it to your chest as you do your crunches. Go for the burn with high weight, low reps to get the 6-pack look. Pecs will respond well to high weight/low reps in a bench press configuration, again, going for the burn. To enlarge muscle mass, always go for total exhaustion of the muscle with high weight to force growth. You may need to invest in some weights and a bench, but the you should be able to reach your goal with just those two pieces of equipment.