@turquoise-- I'm not too sure about acne but it might be worth a try. I know that lysine tablets are a great supplement for herpes. Lysine reduces outbreaks and speeds up healing time by strengthening the immune system. Since acne is a bacterial infection, I'm think lysine will have some benefit.
Depending on what you're taking it for, anywhere from 600mg to 1200mg can be taken daily. I think around 1000mg is more effective. But you might want to start with a low dose of around 600mg and slowly increase it over several weeks.
Also, just listen to your body. If you get results at 600mg, you don't need more. Higher doses of lysine can cause stomach upset in some people.