1.the most important way to avoid acne scars is to avoid acne - means "treat it at the earliest"
there are very effective medications -topical(creams) as well as oral (tablets)- to treat acne and thus prevent scars;
2, once you develop pigmented scars post acne , sun avoidance is of utmost importance along with depigmenting creams and Chemical peels, which your dermatologist may prescribe.
3. for depressed scars, micro-needling, Fractional Lasers, Punch excision and chemical peels may be done as per your skin type, age and finances.
Be Well till next time
Yours
Dermatologist