FB.ui(function () {
method: 'feed',
name: 'whatever - usually site name',
href: 'link back to the site',
link: 'what shows up by the caption',
picture: 'image you want to share',
caption: 'what shows up at the bottom of the image',
description: 'shows up where you would type the status'
}, function (response) {
if (response && !response.error_message) {
// it works!
} else {
// nope...
}
});