I wanted to have anal sex with girls from the time I was 12 or 13. I just always loved the curve of their hips and cheeks and the smooth soft skin... and the dirt little secret that was contained within! I was probably 21 at the time with a long term GF where it was long distance as well (being away at college.)
It was a process to get started with anal. We had each only had one (limited) partner before and I first broached my intention to play with her ass after we had had sex on her parents couch. We were lying there with her on top of me and I cupped and stroked her buttocks as we kissed and talked. I slid my hand between her cheeks and slowly stroked her asshole as I said 'I can't wait to explore ALL of you!' Nothing more was said or done that night, but she later told me it 'freaked her out!'
A few months later we got a motel room to screw all day - she lived at home and couldn't stay out all night. I had bought a small jar of vaseline and hid it in a bag or something. We had sex a lot and she was a pretty easy cummer so we just kept switching around what we were doing. I started with my plan to have her lay down on her stomach and I massaged her back and legs and butt. Eventually I was spreading her cheeks and touching her hole, massaging her gently. She knew what I was up to but let me continue. I awkwardly reached for the vaseline hoping I didn't break the mood and have her rebel and get up, but she didn't. I used some to massage more and slowly penetrate her ass, eventually working my whole finger in. I poked around and I think we also had a vibe working on her clit, or maybe she just used her fingers. Anyway, she worked up to a very strong orgasm with me probing her deeply and finger fucking her cute little ass. Later on when we talked about that day, I asked what was her best orgasm out of the 10 or 12 she had and she mentioned THAT one! I was in heaven hearing that!
In another few months I had my sisters house alone for a few days when they went away. My GF came over and she lied to parents in order to spend one over night with me. So on my sisters waterbed ( who is a VERY religious person ) that night we tried anal sex. After thoroughly probing and loosening her up I worked my way inside slowly, waiting for her to accept me. I don't think I moved much at all that first time, but OMG did it feel so good, just holding myself inside of her, feeling her tightly squeeze me! She didn't cum, and even told me later that the first time hurt a bit even though I went so slow. I asked her why she let me do it again and she said that vaginal sex hurt the first time too, and that sure got better, so why not with anal?!
From then on we had anal probably 50/50 with vaginal sex and we'd play with her clit to have her cum during it. I've been addicted to it ever since.
Sorry for the longer story, but those are some fond memories...