Not all sports shops, demon.
Some of them have treadmills which test your running pattern, how your foot lands and rolls, etc.
If you don't have one like that near you (asking at your nearest sports centre may help), ask the shop if they can advise you about the best shoes for your foot.
They should ask you to walk up and down in your socks, and watch your feet.
If they just ask you to try them on and see if they are comfy, then they aren't fitting you up properly.
If you're enjoying running (Yaayyy!) then if you have an iPod, try this ...
I started to find that there were some songs that were easy to run to, because the beat precisely matched my normal running pace.
I then made a Playlist on my iPod, just for running. All the songs in that Playlist are exactly my running pace. It's like having a subconscious metronome. It really keeps me going, because I know if I'm flagging, because I fall out of time with the songs.
My running pace, by the way, is 160 beats (or paces) per minute.
For a perfect example of a 160 bpm running song, try I Said Never Again by Rachel Stevens.
It does work ... honest !!!