One of the things that makes for a good shopper is the ability to compare shop. This basically means that you see something, you like it, but instead of buying it you search around for the same item sold cheaper elsewhere. It's pretty simple, but you have to know your shops and have patience.
For example, Urban Outfitters has these cool scarves for $24:

I don't know about you, but $24 is way too much to pay for a scarf, especially when Bliss Accessories has them for $7.99!

They're EXACTLY the same, let's take a closer look:

Comparison shopping pays off, shop around and save your money!