Having freckles is genetic, but their formation is triggered (or exacerbated) by sun exposure. While you cannot get rid of them completely, a good way to keep more from forming or to make the ones you have less noticeable is to stay out of the sun and wear sunblock daily -- rain or shine. I would recommend an SPF of at least 30.
Sometimes freckles fade over time; I used to have a ton of them when I was younger, but they've all disappeared. I kind of miss them!
Yes! It's so weird -- I had never noticed until recently -- but I saw a picture of myself from grade school and thought, "OH, right, I had freckles..." but they're gone, and I never noticed when they faded. I'm 29, and I know I had them as a teen -- but I can't remember seeing any for the past decade. So bizarre! I think it must have been my religious (compulsive?) use of crazy SPF sunscreen on a daily basis...