Know your plants. Choose what to grow based on your local environment and begin to prevent infestation even before you plant. Research which plants fare best in your area and in soil conditions, and carefully monitor plant health so you'll recognize signs of infestation later on.
Buy organic. Begin with untreated seeds or organic plant starts, and plant them in organic soil. Ask around for a trusted neighborhood nursery or seek out suppliers who have demonstrated a commitment to growing organic. Keep an eye out for providers who've signed the Safe Seed Pledge.