This is a common question, but thankfully one that has a logical answer. What most people tend to forget is that wine is a living, constantly evolving, organism. Think of it like an Olympic athlete, once it reaches its peak of physical fitness, how well it maintains that level determines its career. Any injury it gains along the way (no matter how minor) might cause repercussions further down the line, or end the career entirely. The best way to look at how to avoid problems is to assess what the elements are that cause them, so here are my three easy steps for how to kill a wine:
1. Leave a bottle in the kitchen, by the oven. Although storing a wine in an environment that is too hot or too cold will cause harm, it is a frequently changing temperature that will really do the trick. Usually this will cause maderization (the wine smells and tastes like Madeira, but is more vinegary and unpleasant), also the cork will be pushed out of the top of the bottle and may cause some wine to bleed out.
2. Slot the bottle into the port of your subwoofer, or in front of your biggest loudspeaker, ensuring that you maintain a constant output of loud music at all times. Vibrations will damage a wine over time; any big shocks or jolts to the bottle will also cause harm. If you look at the history of wines imported to the UK, before rubber tyres and good suspension were invented, the three major regions were Bordeaux, Porto (for Port) and Jerez (for Sherry). Merchants at the time argued that the wines were actually improved by the gentle movements of the ships over the waves.
3. Leave the bottle by a south-facing window. Other options include in a greenhouse, or on the parcel-shelf of a car on a hot day. UV will also damage a wine, which is why most top-end wines will have very dark UV resistant bottles. It is also the function of the orange cellophane that Cristal Champagne is wrapped in.
My best advice for those without a cellar is usually to store wine in the cupboard under the stairs; it is generally the most stable in temperature, quiet and dark. A north facing room with no windows will often do the trick too.