Ultimately it depends on what you're shooting and how happy you are about the photo you took. If the photo pleases you, then it's a good photo. You don't always have to have approval from a professional photographer when you're not using professional equipment.
As for exposure ore sharpening - is that a term in itself?
Exposure is about how well lit the scene is through the different parts of the photo. You can have the clouds well lit but the ground is dark or a night party with faces well lit but the dj is in darkness.
Sharpening - how defined are the lines or the objects in the photo? If you take a photo of a person, can you see their hair well defined? Or do you blurred photos?