1. Do not switch your foundation to the season
Even if you are not as super dedicated to tanning in the summer, your skin color may vary slightly depending on the season. So make sure your foundation's choices reflect this - if you use the basics you usually use in winter summers, it may look a bit too dark.
2 with your hand back:
Common mistakes in the face make-up use your back to find your base shadow. This does not work because if you put your hand on your face, it probably will not match. So why do you use it to find your base shadow? So, if you can, try to find some foundation on your jaw to find a real match.
You can buy your own De'Lanci cosmetics