There is a huge industry out there selling sports shoes. It is quite daunting. Do remember that there is good evidence that injuries are more often caused by the shoes a runner wears than by the action of running.
There is plenty of evidence to demonstrate that many running injuries are caused by people wearing worn-out or unsuitable running shoes. Our opinion is that strength in feet and stability are also very important factors.
The general advice is that trainers have a shelf life of 300 to 500 miles, after which they lose their support and cushioning and need to be thrown away. You should make sure that you visit a specialist shop when you buy a new pair, as requirements differ. It is natural for most people's feet to roll inwards (or pronate) when they run, but some shoes don't compensate for this. If you wear trainers that cause you to over-pronate, you may be at risk of backache, hip pain and knee problems.
At Supplefeet Enfield we recommend Saucony and New Balance trainers. We also advise patients to go to Runners Need in Liverpool Street for current, excellent advice on trainers for you.
Supple Soapbox - Kids trainers are fine in moderation. They are not appropriate for babies - wear classic children's shoes like Start-rite please.
For older children, get them fitted where possible with shoelaces tied up please.
And top Supplefeet Tip = Butterfly Lacing.