How do I best store wine?
First, if you are buying wine to drink within 3 to 6 months, you can stop worrying about storage right away.
If you do keep wine for years on the other hand, the manner in which your wines are stored is important if they are not to deteriorate early.
Ideally, they should be stored in a dark slightly humid place with a constant temperature of around 8-10°C.
For bottles under cork, store lying on their sides with the the wine fully in contact with the cork.
For bottles under screwcap, I tend to prefer storing upright.
If you have a cellar available then this is probably the best place to store wine - providing there isn't a central heating boiler located there!
It is a shame that in England house builders do not provide cellars in houses - unused space that does not affect our visual landscape. Coming from Switzerland, where cellars are common even in apartment buildings, it was a source of consternation when I moved to the UK. The existence of a proper cellar was one of the reasons we bought the house we are in.
Cooler is better, but if you can't have the ideal storage space, what you want to try is find a place with the least temperature fluctuation. You want to avoid high temperatures as well as very cold ones, but once within a reasonable range you want stability more than anything - as all change "tires" the wine
Light is also a problem and can affect the flavour of wines, this is why many wine bottles are dark in colour. Under no circumstances should wines be stored in direct sunlight.
It is of course possible to get carried away with all this. Being realistic, in a modern house, a good compromise is a wine rack in a cupboard under the stairs where the temperature is reasonably constant in the range 10-16°C. If no cellar, use the coolest room in the house.