How can you best get a lot of muscle definition?

Aerobic: Your definition is 90% a reflection of having very little body fat. A man doesn't need any more fat on his torso than is on the back of his hand. Notice mr. Reynolds' muscles are not especially large but he has basically no subcutaneous fat. You achieve this by cardio and eating smart. Very glad you're pursuing a fitness lifestyle -- best wishes.

Exercise/Nutrition: Weight training generally helps to shape and tone muscles while cardiovascular exercise burns the fat around the muscles so you can see them better. Lighter weights with higher reps are better for tone, and heavier weights with fewer reps would be better for size and strength. So you need higher rep exercises, regular cardio and diet of lean protein and complex carbs.