How t start a conversation with a girl please answer ?

IM really in need of a girlfriend I am out of school and everyone at my work is really old like 40 50s IM 18 almost 19 and am feeling lonely I haven had a girlfriend in about 7 months and I want to find one but don't know how to start a conversation with a random girl like lets say I was at gas station Like 7 -11 what do I say to start a conversation Like last week I was at home depot looking for a paint to put on a bike IM restoring and saw this girl but I didint know what to say to her and she was right next to me also if you don't catch them looking at you is that an indication there not intrested in you