After saving Earth from V'ger, Kirk and Spock managed to escape Starfleet's smothering celebration for one day of relaxed touring. They walked across the Bridge, shared tea at the Japanese garden, and barked back at the sea lions--and all day, Kirk wondered how best to pop the question.
He considered mentioning their years of friendship, their obvious compatibility, or their shared interests.
Another idea was to casually ask Spock about his dream date.
They stood at Lombard Street. "Such a winding, indirect route is illogical," Spock observed.
"Spock, will you marry me?"
"Yes, Jim. Of course."