Adobe photoshop is one of the most powerful photo editing programs used for a while. Although its a extremely useful tool there may be some learning curves. There are multiple ways to draw in photoshop. First things first making a file in photoshop. If the drawing is being made entirely in photoshop press create new, choose the document size and press create.
If half of the drawing or photo is being made on paper or another media press open locate the photo then continue from there. After loading the photo into photoshop have a color pallet planed or use existing colors from the photo. The next thing to do is locate where the lights are aimed and how it interacts with the objects in the photo. Lets say for example a flower sitting under a table lamp. The light from the lamp would be a almost white color. This is because the further away a light source is the more color will show. But this may not be the case for all lights as things like neon lights and florescent lights.
The next thing is the shadows, shadows usually follow the light. When choosing a color for shadows blue would normally be the best but sometimes choosing the opposite color would work well. The light and shadow should also match the mood of the drawing. If its bright and bubbly make the drawing bright, If its a dark and edgy make it dark. Shadows should help make the drawing work.
Now for some more practical things. In the image below theirs a screen shot of a layer set to hard light, this is where “filters” are applied.
The Photo below of the pumpkins is an example of this of some pumpkins and a drink in photoshop. The layer selected looks purple but in the photo has a green tinge. It appears green because of the filter selected. This is why filters are important.
These can affect the mood of the photo. The filter selected in the photo below is set to subtract, If this where to be changed it would become more purple and can change how the entire photo looks. These where only tips and tricks that can be used, now after everything be sure to be creative.