Including a post title in a twitter link

The problem is that get_the_title() will pass the title through a filter that texturizes the quotes. So a regular ” becomes a curly quote (“) and urlencode() will break it.

So instead, write your own title function and use that:

function my_get_the_title() {
    global $post;

    return $post->post_title;
}

This should bypass any unwanted filters and let you work with regular quotes.