In order to make your foundation look natural and last all day long, you need to take good care of your skin first.  Healthy skin translates into flawless makeup! So, here is how to do it:

Skin Care:

Always wash your face mornings and evenings with a gentle cleanser. Never use soap, by doing that you will dry up your skin.
Never go to sleep with makeup on. Make sure you remove all makeup from eyes, lips, neck and face before bedtime.
Use a night cream to keep your skin well hydrated overnight. Don’t forget to use an eye cream twice a day to keep this sensitive area fresh and young looking.
Exfoliate your skin frequently to remove any dead skin build up. No matter your skin type, this is a very important step to do.
Always use products according to your skin type for better results.

Skin prep for makeup application:

Always start with a clean and moisturized face. Make sure to put extra moisturizer in the areas of your face that tend to get more dehydrated.
Use a face and eye primer to prepare your skin for makeup.

Foundation Application tips:

For a flawless foundation you need to find your perfect colour match. If it is too light or too dark you will not get good results. Always check the foundation colour along you jaw line. The perfect colour will match your neck and face, and it will look smooth on your skin.
As with skin care, use a foundation according to your skin type at all times.
Always apply foundation in the back of your hand not directly to your face, that way you will have more control of how much coverage you want, it will be easier to blend and it will prevent foundation from getting cakey.
I recommend using a foundation brush to apply your foundation all over your face. After that use a damp beauty sponge to go over and blend even more to achieve a very natural looking finish.
Always remember to blend your foundation down to your neck.
To make sure your foundation stays fresh all day, use a translucent setting power. If you want extra coverage, you can use a tinted setting power or a foundation power that matches your foundation.
Finish your makeup application with a setting spray to bring back moisture to the skin or use mattifying setting spray to control oil from building up.