According to wikiHow, "A person's kissability can be negatively affected by many factors, including bad breath and chapped lips. However, there are plenty of things you can do to minimize these problems and make yourself more kissable."
Here are the steps:
Have fresh breath.
Make sure that your lips are well moisturized.
Don't forget to look after your skin.
Make plenty of eye contact.
Make sure to look at your (future) partner's lips every once in a while.
Ensure your mouth isn't carrying a river of fluid!