Great compilation of advice from Ashe Dreyden. Tech-centered but a lot of it is very applicable to academice conferences, too.
The easiest way to get feedback on your efforts is to publically state what you've tried and ask for contructive criticism. Be transparent and truthful. I've seen many conferences write blog posts about what they've done to address the issue of the lack of diversity and the positive or negative results that they ended up with. This is important for a few reasons: it signals that this is important to you and that you are open to more ideas as well as letting people within marginalized groups know that you are considering their needs and the reality of their situations.