I am sure this will become a regular feature as there is so much to learn and go through with Photoshop so lets start with some basics:-

1. Do not work on the original image. Instead create a duplicate layer and work on that. This way you can always go back to the original with no loss.
2. Do not sharpen until you have finished all other work on the image.
3. CTRL/CMD M brings up your Curves.
4. CTRL/CMD U brings up your Saturation Box
5. CTRL/CMD J creates a new layer.
6. Go to Image>Adjustments>Shadows/Highlights. Make sure “Show more options” is ticked and have a play.