First, know that you will have to be patient if you want a properly aged cigar. You will have to age your cigars for about a year in order to achieve the flavors and complex subtleties of a well-aged cigar. Also, know that in order to achieve the rewards of a well-aged cigar; you must begin the process with a high quality cigar. If you try to age a lower quality cigar, chances are any amount of aging won't improve their flavor significantly. Many high quality cigars that you find too strong or odorous are perfect candidates for aging. In fact, almost all high quality cigars can be improved through the process of aging.
To age your cigars, purchase a good quality humidor. Cigars must be stored in a constant and stable environment. Follow the 70-70 rules. That means the humidity must be at a constant humidity of 70%, and at a temperature of 70 degrees Fahrenheit.
Of course, the environment in which they are stored is crucial. Follow the usual 70-70 rules for temperature and humidity. Any more and your cigars will get moldy; any less and the aging process begins to be stunted. Maintaining a stable environment for your cigars is key - a constantly fluctuation environment can be disastrous. Swings in temperature and humidity cause cigars to expand and contract, cracking their wrappers and it may disrupt the aging process. Ideally, the space in the humidor should be about twice the volume of cigars. The lining should be cedar - cedar wood is highly aromatic wood, full of its own oils. With the passage of time, the interaction of the tobacco oils amongst themselves, and with the cedar oil of the wood it leads to a mellowing and blending of flavors resulting in that subtle complexity you can only get from proper aging.