Don't abandon your tyres somewhere in a corner - you won't do them any good that way!
Before changing your tyres, use a piece of chalk to mark the running direction and where they were fitted (e. g. lf = left front wheel; rr = right rear wheel). Then clean the tyres thoroughly, removing bits of gravel. Tyres should be stored in a dry, cool, dark room away from oil, petrol, grease and any other chemicals, as these attack the tyre compound and can therefore drastically reduce the service life of your tyres.
Tyres on rims should never be stored standing up - they should be hung up or stored lying flat (ideally on a wooden pallet).
However, tyres which are not fitted on rims should be stored upright and turned slightly every four weeks to avoid pressure points occurring. They should not be hung up or stacked on top of one another.
If you wish to avoid the effort this involves, many specialist tyre dealers offer a relatively low-cost tyre storage service which ensures your tyres are kept correctly.
Before putting your tyres back into service after storage, you should have them checked for damage and wear, and also to assess the remaining tread depth and any potential imbalance. This is a service offered by all specialist tyre dealers and helps you to avoid uneven wear.