How to have anal sex?

Me and my girlfriend have talked about anal, and we want to do it. I lost my virginity to my ex, and it was VERY awkward throughout the whole act. I really like my current girlfriend, and I want not to be awkward. How should I go about taking her clothes off? I have fingered her a few times, but her pants were on the whole time. We have been ontop of eachother a couple of times and it was really passionate (not akward at all). Any tips for the undressing and actual penetration?