I've had my fair share of foundation flubs and have gone through dozens upon dozens of foundations over the years. Here are a few tips to help you find your perfect foundation and how to make it look flawless.
Find the right color
This is somewhat of a trial-and-error process and it may take a few tries to get it right. I myself found that most of the drugstore brands tend to be too orange on me so I had to go to the makeup counter for a more perfect match.
How to find a match: going for the right tone is the most important thing. I have a more yellow pallor so I choose foundations that are yellow or olive toned. If you have a more rosy complexion, go for cool toned foundations. Test a little on the underside of your wrist, where your tan line starts to appear. If the foundation blends into your skin, it's the right tone.
Find the right shade
Too light and you look like a ghost, too dark and you get a makeup line at the side of your face. Your skin is most likely dark in some patches and lighter in others--otherwise why would you need foundation? Find a shade that is between the darkest and the lightest--a happy medium--that way it should blend the dark areas with the light. Don't change shades between summer and winter, either. Use a light-weight bronzer for summer to warm up your complexion to match your new tan.
Make sure your concealer matches
Your under-eye concealer can be a little lighter than your regular skin to get rid of circles, but your spot concealer should be spot-on in color. Make sure it blends into your skin. It is just as much a trial-and-error as foundation and you should test the color on your arm first.
Choose a foundation that works with your skin
Whether powder or liquid, your foundation should choose one that has moisturizing properties if your skin is dry and matte-ifying properties if your skin is oily. I have oily skin so I choose powder foundation in an oil-free variety. If your skin is prone to dryness, go with a moisturizing liquid foundation.
Blend, blend, blend
Whether you go liquid or powder, you have to blend the lines at your jaw, the side of your face and anywhere the foundation stops. Make sure you make it so that the foundation completely blends into the skin so that there is no dreaded makeup line.
If you follow these tips, you should be on your way to a beautiful complexion in no time!