The age old debate of do I apply concealer before or after my foundation? Is still being discussed, but quite frankly, my reply is you conceal AFTER applying your foundation.
Just think - You spend lots of time concealing your blemishes, dark shadows, under eye area and then you rub your foundation on top rubbing off all your concealer needing you to conceal once more on top of your foundation again! - Why not take out having to conceal twice by just applying your foundation first and your concealer on top?
The next question is Where should I apply concealer?
My video answers that for you, and wow, what a difference it makes!
If you use a concealer that is too light under your eyes then you will get the 'panda eyes' finish, which will show up best in photographs once the light from the flash reflects off your concealer (never a good look)
You need to match up your skin tone and find a concealer the same colour.
OK, so a lot of make up brands only have concealer in light, medium or dark (none of these will be perfect for you) so you may have to search a little further for your tone colour - remember the tips from choosing your foundation, if your base colour is pink - you need a pink based concealer.
I like to use both Supercover and Dermacolor concealing palletes - although you will only need to have one colour, all colours can be brought separately.