So you want to write a kissing scene, huh? Well, sit down children and allow me to inform you.
Alright, this is a biggie. How do these two get close enough to kiss? There are many ways to do this and each one has its benefits. If the closing is slow and steady, this usually indicates a soft/passionate/unsteady kiss. However, if the closing is fast or sudden, this usually means a hard/assertive kiss (possibly from months/years of romantic or sexual tension).
Sight: Sight is probably the easiest of the senses; simply write what is seen. If you write from one character’s point of view, write what they see.
Sound: This could be either background noises or a character’s heart beating or anything else. If the kiss continues, you could possibly include soft moans or other noises if they seem appropriate to your character.
Smell: Describe what your character smells. It could be the way their perfume or cologne smells, or you could describe their natural scent.
Touch: This is an important aspect to describing the kiss. You could choose to describe how the character’s skin feels. Or you could describe how the character’s lips feel against the other character’s.
Taste: Taste has a very broad range and is generally not as easy as it sounds. There are many description words and tastes to use. It is important to the mood what description you choose.
Heads: Most people tilt their head when they kiss. Of course, your kiss does not have to happen this way. Usually when characters do not tilt their head it creates awkward bumping foreheads, which could be what you want if you want an awkward first kiss (these are effective for teen kisses).
Eyes: Eyes open or closed? Open creates either an awkward or tender kiss. While closed creates a passionate or pleasurable or just about anything kiss.
Noses: Noses are invading appendages that get in the way of perfect kissing. Henceforth, no kiss is perfect so don’t write them that way. Noses will always get in the way. Even when your characters tilt their heads, noses can still brush the side of their faces. Now, your characters will probably not notice them (unless they’re the type to notice everything) unless they have an awkward kiss.
Lips: LIPS! You’re writing a kissing scene, of course lips will be important to the description. Are they soft or hard, chapped or smooth, is your character even a good kisser? You could also include if maybe they taste like some kind of food, or if they are wearing chapstick. Lips are important.
Tongues: First kisses usually don’t include tongue; neither do quick kisses. Think about what type of kiss you’re trying to convey
Breathing: Your characters are human (unless they aren’t). They need to breathe. But how has the kiss affected their breathing?
Bodies: Bodies are stupid, messy things that bump and rub and bounce. How are your characters responding to the kiss? Are they pulling closer or pushing away? Are they clenched tight or flowing loosely?
Hands and Arms: During a kiss, hands could be floating in the air (awkward or surprise kiss), or they could be everywhere on the other character’s body at once. Possible places to put hands that are not on the other character’s body could be surfaces near the characters, the character’s own body, or they could just be in the air. But if you’re looking for contact, they could be running their fingers through the other character’s hair, holding the back of their head or neck to keep them close, rubbing their back (or further down), or just wrapping their arms around the other character.