I use Revlon concealer for the undereye...apply with sponge applicator thingy, leave for a moment or two to semi set then lightly press and roll with a finger tip. Then apply ur foundation as normal.
As for bags...well...I remember being 19-20-21-22-23-24 and saying I will never get them...HAH...the amount of sleepless nites/weekends/weekdays I had they were always going to be inevitable. So my answer for all of you is SLEEP.
To reduce puffiness use a table spoon rinse under cold water & place on eyelid till no longer cold...works a treat.
xxV
hemmaroid (sp?) cream helps constrict/reduce the blood vessels under the eyes therefore helping them look less puffy, red or tired. But for dark circles your best bet is to find a very peachy/apricotty toned concealer which will actually neutralize the color of the dark circles. If your wearing it with foundation I would apply it after foundation (if you do it underneath it all just rubs off when you put your foundation/base on). Use it on the inner half of your dark circles and pat/tap gently with your ring finger to blend it into the skin, I often do a couple of layers (leaving a min or so btwn each one, but go easy on the amount coz a bit of darkness under the eye looks much better than creased and obvious). Good concealers many people swear by are laura mercier secret conclear and bobbi brown, but mostly its trial and error and seeing what works best 4 u.
i really like this product: http://goodtobeyou.com/liftupeyegel.html
it has light reflective qualities in it. also, plenty of water and a bit of concealer always help too. if they are brown or sallow dark circles, try something with a pink tint. if they are blue, then get more sleep and water, and get a concealer that matches your skin tone.