I agree on the use of the tea bags, if you use chamomile and green tea around your eyes morning and night it might help. They can also be used much like a toner on a cotton ball, or an extract of these herbs can be added to your eye cream.
If you have gone through the list if things aready mentioned; sleep, allergies, food etc. you are already on your way. Stay away from MacDonalds, fast food, and any highly processed foods, at least minimize intake of them for a period. Don't eat sweets every day, and no coke or sodas. This might be the hardest if you are used to white flour, burgers and sweets during the week. Try to drink four-five cups of green tea every day and stay away from coffee for a while. Girls could also try a diet suplement with vitamin K (in a multivitamin is not a bad idea) and check your iron levels. A good thing is to choose a periode for about a month or so, even better three months, where you really stick to your plan. That makes it easier to be motivated and by the end of the period you can valuate the results and see if the action taken are worth the effort.
Light exercise every day is a must, 30 minutes walking, on your bike, with the dog, twice a day or some thing at the gym now and then. This often comes naturally in a normal day, but if you spend a lot of time reading, writing, studying, online,TV....you might have to look at how some light activities can be added to your every day. Just ask a masterstudent or someone writhing a Ph,D how this show up around the eyes (lol).
There are some ingredients that are efficient enough for dark circles under the eyes to be worth trying in a eye cream. They tend to be rather expensive, but luckily there are very good products available that are in the afordable price range. If you want the best ingredients and not at a high end price try some of the do-it-your-self skin care sites on the web. This is my best discovery the last two years, and it makes it possible for me to try the most efficient ingredents in all the popular brands.
One of these ingredients is called Hesperidin Methyl Chalcone, it is extracted from lemon peel and works by streangthening the fine capillaries in the eye area. The reason for dark circles under the eyes is because red blood cells get trapped in the fluid between the cell and this will streangthen capillaries so that they don't leak red blood cells. When the body brakes down these blood cells the biproduct leaks out to the surrouning tissue and discolors the thin skin under the eyes. This is also much the same way vitamin K is supposed to work.
Another important ingredient for this problem is Chrysin (fawnie mentioned this one). Chrysin helps activate an enzyme that speeds up the brake down process of the red blood cells and their biproducts.
Hesperidin Methyl Chalcone, vitamin K and Chrystin are really effective to target this problem. Together with certain peptides (sort of "pre-proteins" ) these ingredients has showed to lighten and even remove the darkest of circles in the eye area. Hyaluronic acid asists in this process too.
However this is not the only possible reason for dark circles in the eye area. It is possible that the pigmentation production in the skin is overly active and cause the dark coloring. The mentioned ingredients Hesperidin Methyl Chalcone, Vitamin K, and Chrysin will not help this problem. Then different ingredients are needed. Liquorice extract, vitamin c, alpha lipoic acid, green tea extract, Niacinamide (vitamin B) are some well worth trying in a cream.
Dark circles under the eyes are often hereditary, just look at your mother, father, siblings, aunts and uncles. Dark circles are very common, all most every body has them from time to time, extremly dark and cronic circles are less common at least in young people. Do not despair over this, they are most likely not as bad as you think, and there are very likely something that will help you. It is a sort of thing that can take a bit of trial and error before you find some thing that works for you. Often it is just a few simple tricks that when combined will resolve the problem.