Thank you Elliot for asking a great question!
Before you consider covering up your dark circles it's probably worth pondering for a moment why you have them and if there's anything you can do to help the situation.
There are whole bunch of possible reasons why you have dark circles under your eyes (not being medically trained I'll just stick to some of the non life threatening reasons!) If you ask most people (usually mums) they'll tell you it's down to late nights, lack of fluids or staring at computer screens or game consoles for hours on end. Sound familiar? However it could also be due to allergies irritating the eyes and making you rub them, nasal congestion and sinus pain or skin problems like eczema. I have also read that for some people it's down to a lack of certain vitamins or iron deficiency.
The most common reason for dark circles is ageing. The area around your eyes is very sensitive and as you age the fat pad and skin under your eye gets thinner which means the blood vessels under you eyes become more noticeable. Something else to consider is the tone of your skin sometimes it just comes down to genetics, dark circles can run in the family!
There are a number of products on the market for men and women that boast the ability to hydrate the skin around the eye therefore diminishing the look of dark circles and puffiness. I can't really recommend a product as I've not found one I can say really works. Under eye gels or creams are usually cool and are therefore soothing but I'm not in favour of loading the eye area with too much product because as a contact lenses wearer I'm very aware of how products can work their way into the eye. In fact this is especially true at night and that in it's self can create puffiness or irritation.
For a more natural approach I favour applying either cucumber slices, almond oil, chamomile teabags (leave in the fridge for 15 min before use, to cool) or witch-hazel neat on to a cotton pad, leave on the eyes 10 mins whilst taking a good old fashioned rest. (Stress is also considered a trigger for dark circles)
When it comes to covering up dark circles, there's only one thing for it and that's concealer! First moisturise the skin but please, not too close to the eye otherwise you risk the moisturiser entering the eye. Then use a light covering of primer this will help to smooth the area and will ensure your make up stays on longer.
Now you need to apply the concealer. The best way to add concealer around the eye is with a small brush and a little finger. Pat the make up on to the area and use your little finger to warm the product up and even out the distribution. It's very important that you add only very small amounts of product and if necessary layer as needed. Dot the concealer on rather than drag the brush along the dark area as this will just help to accentuate the problem. Make sure you blend out edges for a more natural look. I suggest you set the concealer with a very fine covering of the finest powder you can find and if in doubt go for translucent every time.
The colour and density of the concealer you use is very important. It needs to be rich in pigment but not too heavy. The colour should correct the area by bringing it up to the same tone as the surrounding skin.
I advise you to don the mantra 'Less is more' when working under the eye to keep it looking as natural as possible. It may take a few attempts to get the look you want but like most things it's all about practice.
Always be sure to clean any make up off before you go to bed. Be kind to your skin, don't be tempted to pull the under eye area when cleaning. Be gentle and use an oil based eye make up remover for best results.
I promise to post some pages on 'concealers' and 'oil based make up removers' that work, very soon.
I hope I've answered your question?