Actually, I have never had a problem fitting heels. My sole problem was, in fact, with flats. This is largely due to the fact that i tried on the heels before I purchased them. I walked in them in the store, later in the day when my feet had swollen a bit. The flats I bought without trying on first. Since shoe sizes (lasts) vary by manufacturer, one can never know for sure what size will fit unless you have tried on shoes from that manufacturer. If you buy by mail, walk in them on a rug and return them if they are the wrong size. That way the bottoms do not get scuffed.
FINDING YOUR SIZE:
Payless Shoe Source gives its sizes in inches as well. This makes it simple to buy by mail after trying on a pair of men's shoes in a store. You look up the inch measurements of your male shoes and find the female size with nearly the same measurements. You can then order them from the website. You can even buy a gift card in the store to use on the website and avoid your own credit card, if that is an issue for you. Their sizes tend to run a bit large, so you may need a larger shoe from other sources.
There are adhesive shoe pads that can be inserted to keep your heel or ball of your foot from moving and make a slightly large shoe fit. This is particularly handy if you are out of the half-size range of a shoe.
You often need a larger size in a high heel than in a flat. Do not crush your foot or you can end up with irreversible damage or at least a trip to the podiatrist. In addition, the curve of the sole in a high heel is critical. I have two, nearly identical spike heeled sandals with different curves to the sole. One pair I can wear all day with no foot pain. The other pair goes on fine but within two hours my instep hurts and I need to take them off. I would not buy a pair that hurt when I first wore them, though leather shoes can stretch. Quality makes a difference for both fit/comfort and longevity but, perhaps most important....your heels will not break off due to your weight. This can happen with overloaded, cheap heels. You can tumble and be injured, not to mention humiliated. If you are lucky you get to walk home in your stockinged feet carrying your heels...assuming you can still walk.
These About.com links can help find your shoe sizes. Look around there because there are lots of useful charts/articles.
http://shoes.about.com/od[...]eet.htm
Finally, find a website that teaches you how to walk in heels and do not start with 4-5" heels. Get "training heels" first until you can walk safely in them on smooth floors, rugs, carpets and up and down stairs. Then increase the height of your heels.
You are ready to go out in heels when you are completely stable in them indoors. My standard is when I can dance backward while intoxicated I know I will be ok in public when sober or after a couple drinks on a night out.
"A live lived in fear is a life half-lived." - Native American proverb.
"Inside every man is a woman who was drowned in testosterone before birth". - Wendy Jeanette Larsen
"It is better to be hated for what you are than loved for what you're not." - Andre Gide (French writer)