What do you want to conceal? How you use concealer depends on what you want to hide, and where it is on your face. There isn't one product that can do everything, unfortunately! You also have to be skilful in how you apply concealer. If you do it incorrectly, you can wind up making your flaw more obvious instead of hiding it.

Wherever you want to use concealer, the basic rules are:

• Apply it sparingly.  Good concealers are opaque and pigment-rich so you only need a little.  Too much can easily look cake-y.  You can always add more if you decide it's not enough!
• Apply it only on the blemish or shadow you want to conceal, don't spread it out. 
• Pat, don't rub
• If you're using a concealer brush, dot a few dabs of product on first, then blend.  You may still need to pat with your finger to finish off and blend at the demarcation line. 
• Using a primer under concealer will help it last longer and blend in better.

For years I struggled with the instruction that you should put on concealer first, before foundation.  Every time I tried it, I seemed to wipe off half the concealer in the process of applying my make-up!

These days, opinion seems fairly evenly divided over whether you should apply concealer over, or under.  So you can feel free to pick the one that suits you! 

Personally, I vote for over.  Apply your foundation first, then it's much easier to apply your concealer accurately and blend it in. 

The only exception is where you're using a color corrector, such as a green tinted cream to disguise redness.  These creams are optical correctors and you need the foundation over the top to make them work. 

If you want to disguise dark circles under your eyes, always use a concealer that's been made specifically for the eyes. Anything else will dry out the delicate skin in the eye area, and encourage wrinkles.

A common mistake is to choose a concealer that's two or more shades lighter than your foundation, in the belief it will "lighten" the dark shadows. It's more likely to make you look like a racoon! Your concealer should be only a smidge lighter than your foundation.

Because the eye area is so delicate, always pat (don't rub) on concealer with your ring finger. You should always use your ring finger to apply product around the eyes, because it's not as strong as your other fingers so you're less likely to use too much pressure. Or you can use a concealer brush.

If you have outer eye wrinkles, it may be best to keep your concealer to the inner corner of your eye - don't take it beyond the mid-point. Most concealers are quite dense and will settle into wrinkles, making them look even worse!

That's been a problem for me because my shadows go all the way across. So far the only product I've found that doesn't emphasise my lines is Clinique's "All About Eyes" concealer. I'm also tempted to try Lancome's Effacernes, which seems to be getting lots of good reviews.

Acne and zits are usually a double problem - not only is the skin discoloured, it's also a different texture.

In this case, if you're going to use a concealer, use one that either matches your foundation exactly, or is slightly darker. Yes, darker. Think about it - a lighter shade and you're only going to highlight the spot. Dab the concealer with a tiny amount of product, using a brush, and blend it in lightly.

However, because most facial concealers are on the dry side, you may find it emphasises the texture of the blemish and makes it more noticeable. Sometimes it's better to simply use a more covering foundation over the whole face, preferably with a primer underneath.

All text copyright Marisa Wright.

Photo credits:  Concealer brush courtesy of angel with horns, indecisive girl thanks to SashaW, both on Flickr.