I only date one person at a time. Usually just a shared activity or something to see if we're both compatible. The first few dates probably won't be 'dates' because I don't tend to like spending money just to do what everyone else does, I'll probably take her to a scenic park or out to eat or something of the like. When I meet someone, I will know immediately if I'm interested in them or not and I will place them into a category of potential friend or potential interest. If a girl is a potential interest of mine, I'll treat her a bit differently than I would a friend, I'd flirt with her and make my intentions known. As I learn about her personality, if I think we're going to click, I ask her out.
I've considered dating my long term friends but I can never...bring myself to do it. I always think "Well...If I didn't think that I wanted to date her when I first met her, what exactly changed?" and I could never find a answer. People I tend to find attractive (And my view on what's attractive is very particular looks wise and personality wise I think, as well) I tend to not get as close to, I don't want to present the image that I'm just a friend although that can be easily changed. In a way, I see dating just as an outing between two individuals who are potentially interesting in each other. Dating is supposed to be a time where you learn about a person in general, enjoy spending time with them, and decide if you want a relationship.