Aside from possible flaws with SSL, you can make sure the certificate belongs to the site you're visiting. If SSL is secure, then your data should be secure as well. I'm not too certain on the feasibility of faking certificates, but generally what I've read is if it's signed by the proper authority then it's real. I would do some research first, although I think it's unlikely your data would be intercepted assuming SSL is secure, although I imagine there is a way out there to fake a certificate (without a warning showing up -- definitely make sure the certificate is trusted).
