In a perfect world, all your bridesmaids would have perfect feet, between a size 6 and a size 9, all of medium width and none of them would have bunions, hammer toes, problem arches or black and blue hikers toes.
But this is not a perfect world, so before you select what you think is just the right shoe for all your bridesmaids, be sure to check in with them first. Are there any comfort issues; are they all used to walking in 4 inch heels; does the shoe you love even come in their size?
One simple solution is to request a specific color in a range of suitable styles. If you request basic black, white or silver, those should not be too hard to find. If you want a specific color such as emerald or pale blue, see who carries dye-able shoes in your area or on-line.
If you let your bridesmaids pick their own shoes, they will probably end up with great looking shoes that they will wear again. Keep in mind, however, that if one of your girls typically wears only Crocs or ankle boots, you might want to see a picture of the shoe she selects before you give the go ahead. This is a simple request that you can ask of all your bridesmaids without offending anyone.
I have provided a link to a very complete site that I think you will find helpful at: http://weddings.lovetoknow.com/wiki/Bridesmaid_Shoes