You can obtain SSL certificate and display a seal on your site.
you can go to
www.instantssl.com and choose whats best for you.
Please bear in mind the latest one is EV cert (and yes it does cost more).
I would also urge you to put
www.usertrust.com rating on your site (this is a free service) so that you can let people rate you, what you do etc. This will give your visitors confidence (only if you treat them nice and they give you a good rate that is

).
if the above is not sufficient, pls feel free to ask further.
thanks
Melih