What most naturally follows?

How to know when to kiss on a date
Stare at the person's mouth.
While this might seem a little silly, spending some time looking at the person's mouth can indicate you want to kiss them. Of course, you don't want to look at their mouth only, as gazing into their eyes is also romantic.
Nonetheless, looking down at various points can help indicate you want to kiss someone. You don't have to continuously stare at the person's mouth.