You don't actually need a fancy, expensive cellar to store your wine. If you're like most wine consumers, you'll enjoy your wine soon after you bring it home, so all you need is a cool, dry, dark place away from direct sunlight and free of vibration. A small wine rack will do for a while. Bottles that won't be consumed for a while, whether in racks or cases, should be stored on their sides so the corks don't dry out.
If you plan to buy and store a significant quantity of wine for future use, you'll need a larger space, such as a cupboard, crawl space under a stairway, or portion of a garage or basement. Choose a space larger than you might need initially, because once buying wine becomes a habit, you'll fill the space up quickly.
However, if you plan to include wines requiring long-term ageing you might want to invest in a fully outfitted wine cellar. Once again, overestimate how much wine you're likely to collect in coming years and decide how much you want to invest in storing it. The better and more valuable the wine, the more important it is to have good storage conditions.
Wine can be stored in the cases it's shipped in, but most are cardboard cartons that may collapse under the weight of other cases, so wooden or metal racks or bins are advisable, designed and arranged to maximise cellar space. Place the wines you're likely to drink sooner within arm's reach, stashing your long-term collection behind or below them.
Make sure your cellar is well lit, easily accessible and spacious enough that you have room to manoeuvre. An inventory system is helpful, so you can keep track of the wines you have bought, how much you paid for them, who you bought them from, etc. You might also consider a cellar log to record your impressions of wines you taste at different stages of their development. (See wine tasting tips.)
What to put in your cellar? Well, that depends on your taste and pocket, and patience. Serious collectors include a wide selection of cultivars, plus a selection of champagne, vintage port and other superior dessert wines. Others, who simply want a stock of tasty, affordable wines to drink in the short term will keep an eye open for bargains.
The wine collector knows no greater pleasure than sharing a well-aged 'find' with a couple of appreciative friends; making a wine cellar a truly wise investment.