When taking your photo for a Photo Composite, try to match the direction of the lighting. Whether it is a lamp or the sun, pose your subject so the light will touch them just as it will in your Photo Composite.
Which I guess answers the age old question of which came first... the digital backdrop or the photo? In most cases it is the digital backdrop. This way we can be prepared for our photoshoot.
This photo above of my daughter was taken at a park after we had decided on the digital backdrop. We tried our best to match the direction of the lighting with the digital backdrop to help sell the illusion.
The photo below was taken in my living room with a ring light strategically placed behind my daughter to match the lighting from the window in the digital backdrop. I also had a soft light in front of my daughter.
In the case that you are unable to match the lighting due to Mother Nature not receiving your memo on needing a clear sky. No prob! Choose a lightly shaded area or an overcast day to take your photo and your can add the lighting when you edit your photo with the composite.