How do you get rid of acne forever?

Forever is a long. Forever is a long time - so there is no getting rid of anything that is possible forever. Reducing the burden of acne can involve antibiotic creams, antibiotics (oral), retin a (tretinoin) creams and systemic rentin a are the usual regimens. Avoiding foods that trigger acne (if there are any for you) helps.
Hard to do. Accutane is the gold standard and gives you the most hope.