I used a print out explaining the basic rules on using the levels and curves including some touch up tools in Photoshop to ensure I was applying these correctly to my images, all the information on the hand out included all the tools that I use during my editing, it explain how to apply these to your images during the editing process.
The histogram basically will show how much dark and light tones are in your photograph, so if the histogram is all to the left hand side then there are a lot of darker tones whereas if it was to the right then the photograph is most likely going to be over exposed with too much white in the image, to determine weather or not the histogram is right I must first decide how my image is supposed to look, if there are supposed to be a lot of mid tones in my image and no dark spots or over exposed spots then the histogram should be relatively even across the histogram showing levels in both the dark and light areas how ever if like my images the shot should have a lot of dark tones then the histogram should be to the right mainly and can be adjusted by moving the levels each way to create an even darker or lighter image.
I often used the s curve in my images to create a less flattened tone, I applied this technique when my image was correctly exposed just to give it a more detailed effect highlighting the lighter parts of the image and darkening the darker tones to create a more true black.
The levels can be used to reset the white point and mid tones whereas the curves are able to be altered more subtlety meaning you have a wider area of manipulation.
Clone, Heal and patch tools;
I used the clone tool when using patches on images, it is used to copy an area of the image and apply it else where in the same image so this was useful for covering up blotches on the skin of marks in the background.
The spot healing tool also helps to get rid of blemishes and mark, it takes the area surrounding it and adapts to help cleanse the selected area, the patch healing tool also applies this same technique except it blends the two areas together.
Here I have screen shot me using the tools on my images to manipulate the shadows and highlights, By using the curve tool I was able to move the curve up to create more highlights and by adjusting the bottom left of the curve towards the right this created a more true black, this gave my images the correct highlighting and colour needed.
I also used the clone tool to clone the black of the images over any blotches or marked areas, these included where the background was creased and had captured light.