I usually choose a short phrase from the dialogue or contents of the scene that sums up what's going on, or conveys whatever vibe I'm going for. The purpose of my comic's opening scene (first four episodes) was to quickly introduce the characters and their dynamic, so I felt titling it "Stay Close" would work towards my intended set-up of an overprotective sister trying to keep the family together, while her siblings are doing everything but "staying close". It conveys the vibe of danger and protection I was going for, and I think the main character's whole deal and defining motivation (and inhibition) can be summed up in those two little words I pulled from her dialogue, so it works well as the title for her introduction scene.
I also like using symbols as titles. For example, in one of my written stories, cicadas became a symbol of the protagonist's hometown. When I wrote a chapter where he hears cicadas and is reminded of his longing to return home again, I titled it "Cicadas". The chapter was about the theme of missing one's home, childhood, and lost innocence, but "cicadas" works as a more subtle symbol for all three and isn't as clunky and blatant as titling it something like "Missing Home" haha 
