Get caught looking (briefly) at the other person's lips.
Don't purse your lips. Keep them softly parted — not so much that you could breathe comfortably through the opening but enough that you could bite your bottom lip easily.
Make your mouth appealing. Use chapstick or lipgloss to smooth over flaky lips and keep your breath fresh with mints or spray. Avoid gum which you might have to spit out awkwardly if the other person goes in for a kiss.