First and foremost if your buying running shoes for the first time, attend a professional running specialist shop.
Locally we have two very good shops that can advise you with up to date knowledge. They will assess your running style in store and check the fit of the trainer (you may try many many pairs) before finding the correct fit for you.
www.runninghub.co.uk (Southborough, Kent)
www.upandrunning.co.uk/sevenoaks (Sevenoaks, Kent)
Road runner or trail runner - Pick the trainer for the terrain you will be running in. Road runners/pavement running need to have more cushioning in the sole. If your off-roading then a trail runner is needed to give you more grip and greater traction.
Take the insert out of the shoe and stand on it. The size and shape should match the size and shape of your foot. Your toes shouldn’t spill over the front or sides, if this is the case the shoe is not a going to be a good fit.
Length - you will need an assistant/friend. You need to be standing upright with your weight evenly distributed between both feet and relax. Your trusty assistant can then check the length. One thumbs width of room should be available from the end of your toe to the end of the trainer. This will allow for movement and mild expansion as you run.
Check the snug fit. Lacing is important so make sure they are laced securely. Wiggle your toes and check there is little to no pressure on the pinky toe and wiggle room around the big toe. Slightly looser than the snugness of a watch strap.
Walk (preferably run). Check that your heel doesn’t slip out the back and that nothing pinches or rubs uncomfortably against your ankle bones or achilles.
Repeat until it feels right. Don’t settle for something cramped thinking you’ll break them in, they should fit properly right from the start.
Have your feet measured annually as our foot size can alter as you age.
Take your time to get the right shoe and avoid online shopping where possible.
Try on many many pairs and get different running shoes for different terrains.
Cross trainers are not ideal for running as they offer little support to the mid foot.
If in doubt ask your Podiatrist for their advice and always take any orthotics or insoles you have been prescribed with you to the running store.
Good luck and happy running