If you've ever been out shopping and saw a pair of shoes that you just had to have, only to suffer the disappointment of the store not having them in your size, you know what a letdown that can be. If you're smitten with a pair of shoes, it can be hard not to buy them, even if they don't fit properly. For example, if you're a size eight and the store just has a size nine in your desired pair, while the shoes won't be too large, they will slip off your heels and cause your feet to slide in them. Make the shoes a full size smaller with a few steps.
Place a pair of insoles in the shoes. This will not only make the shoe more comfortable to wear, it will also make them more snug. Opt for a thick foam insole. Purchase the right kind for your shoe size. Some varieties will require that you trim them down to size, which you'll have to do carefully with a sharp pair of scissors.
Apply a foam heel pad to the back of each heel. This will give you around 1/8 to 1/4 inch more snugness. Put on your shoes and assess their size. They'll most likely still feel slightly too large.
Stack another foam cushioned heel pad on the back of each heel pad you've already installed. Put on the shoes. They will feel perfectly snug but not tight. If they still feel too big, stack yet another foam cushioned heel pad on the back of each heel.