Sometimes when you're unsure about an image and you don't really have a final vision in mind it's best to play around a little. Try to add some contrast with curves, or solid color (I like blues) set to a lighten blending mode and drop down the fill, add a black and white adj layer and change the blending mode to soft light, in channel adj. drop the blue slider and up the red slider until it's to your liking; honestly the possibilities are endless. Or a simpler way would be to find some photoshop actions you like, there are tons of free ones, and apply it to the image and see what works.
When you're starting out retouching honestly I feel like the best thing you can do is experiment so you can get a good feel for what works, what might work somewhere else, and what doesn't work at all. It's all about having an artistic eye and remembering(or writing down) what creates a pleasing affect.