The first time they spend the night together is in a tent on M5X-337. It's a learning experience. John wakes in the night to an elbow in his ribs and Rodney's muttered complaints about John's snoring in his ear. He shrugs off the arm that Rodney flings across him a while later and moves as far away as he can--which is, unfortunately, not very far at all. By morning John's bruised shins attest to another new discovery: Rodney kicks in his sleep, though he denies it vociferously right up until the moment that the first shot is fired, and after that they're too busy shooting back and running for their lives.
John returns through the Gate with bruises in odd places, and avoids Carson's eyes during the post-mission medical exam. All in all, the mission's not a success in any way, but John can't quite put it out of his mind. Sometimes when he lies alone in his bed at night he can still feel the warm weight of Rodney's arm on his chest.
The first time they go on a date is in a small boat on P9D-845. Okay, so it's not actually a date. They're rowing to the site of an unidentified something the Ancients left behind, Rodney in the stern with his laptop while John concentrates on maintaining a steady rhythm with the oars. The moonlight on the water rippling out around them reminds John of other nights spent with people he hasn't seen in a long, long time. Romantic, those people called nights like this, though none were as quiet and serene as this one.
It doesn't stay that way. The bottom of the boat scrapes over a rock and suddenly John's doing a lot more bailing than rowing while Rodney yells from behind.
They end up having to swim for it. The shore's not far, but Rodney goes under more than once before John forces him to discard the equipment weighing him down. As they lie on the shore, panting and tangled together, John keeps thinking of other nights that ended in someone's arms in the sand, and quiet gasps in the darkness.
This mission can't really be called a success, either. In the debriefing their eyes slide past each other, as if they have something to hide.
Their first kiss is an accident. It's meant to be ceremonial, three formal kisses on either cheek, but Rodney moves this way just as John moves that way, and their mouths come together, hard.
John can still feel the tingle on his lips after dinner with the Chancellor. He can still see the look on Rodney's face after he closes his eyes and tries to sleep.
The mission's technically a success, even if it feels empty and unfinished. Or maybe that's just John.
Rodney comes looking for him three days later.
Their second kiss isn't an accident but John doesn't think about it much afterwards; he's too busy with what comes next.