I don't really understand the purpose of flat shoes - my top tip for any girl would have to be: Never be seen out of the house in anything other than heels.

Get a nice, attractive hair cut and find the color that goes with you. Change with the hair does wonders! You could also try getting some eye-catching, stylish cloths. Check out magazines and movies that can give you an idea (i.e. Devil Wears Prada) and try and find similar cloths. If you're an American, you should have no problem with finding good cloths, vintage shops in the States are dreamy. And last but not least, be confident. I have met so many girls that are not attractive at all but make themselves look absolutely hot with their confidence. I know you might have heard this many times and it sounds like one of those fake miracle tips but believe me, people are attracted to confidence at a level I still can't comprehend.