All tyre pressures (including the spare) should be checked weekly, when the tyres are cold. 
Refer to the tyre placard attached to your vehicle for recommended pressures. 
This is usually located in the glove box or the drivers' door edge.
Keeping the pressures at their recommended level will provide you with the best handling and ride also keeping tyre wear to a minimum.
Always ensure that you replace the tyre valve cap once you have checked your pressures.
Tyres should also be checked regularly for cuts or any sharp objects imbedded in the tread.
The minimum legal tread depth is 1.5mm. However as tyre performance reduces once the tread depth is less than 3mm, it is safer to replace them earlier than at the legal minimum.
To equalise tread wear it is recommended that the tyres be rotated and their balance checked at every service.
Please see your local  TACC Tyre Dealer for help with any tyre questions you may have.