@Cru123_ besides lysine the only other things are to do like @aurielle said and watch what you eat (some foods trigger it and others can be helpful, like foods that just naturally have lysine in them like yogurt, fish, fruits) also managing stress like she said. Hormone changes can cause them (ex: some are more prone during their periods). Having a healthy immune system helps and keeping your lips safe from sunlight and cold temps can help, I think they even make chapsticks that are meant to help moisturize lips to prevent cold sores (not sure if it works or not). But even just a Chapstick with SPF in it can be helpful I believe.
If none of that works and you get them pretty often, you could also talk to a doctor and get put on antiviralscru123_