Be generous with blush
Wear warm colors
Colors like taupe or purple can look really harsh and dark on webcam. Try to go for warm colors, especially if you have yellow undertones. I like the top row of the Stila In the Light palette and the Urban Decay Naked 3 palette.
Be careful with shimmer
Depending on your lighting, shimmer can make your skin look greasy or your eyes puffy. Try to go for satin or matte finishes if you can help it. I like Lorac Pro Palette for a wide range of matte colors.
Pay attention to dark circles
When you're Skyping, chances are your light source is from above, so look out for dark circles--even if you use concealer, mascara and eyeliner smudges can give the look of undereye darkness, so blot away any smears with a Q-tip. If you have dark circles, try Benefit Erase Paste--a peach-colored concealer corrects darkness really well!
Don't forget to change into a cute top and brush your hair! And, of course, smile--your loved ones deserve to see you at your best.