The article I found helpful and relates to my image with image manipulation techniques is this one:
Image manipulation transforms an image into something else, the article states that there are 10 techniques that need to be noted when trying to manipulate an image. These include: rendering your images, shadows, proportion, texture use, picking images, colour blending, emphasis on detail, combining multiple images, c4d uses, and enhancing an image. The two techniques in particular that are relevant to my image are proportion and colour blending.
The article states that proportion is very important in photo manipulation. In order to make it realistic the objects have to be in proportion to each other. I need to think about this in my image as the photo of the little girl and the photo of the hand holding a cigarette a two different photos and when merged they need to look proportional.
In the article, colour blending is also shown as a technique that needs to be used when manipulating images. Not all images are going to be of the same colour range, saturation or hue so it is important to use colour adjustments in order for all objects in the image to look similar in colour therefor making the image effective. Colour adjustments need to be used in my image because the hand and the image of the girl are different colours.