Relationship hlp, hlp me please ASAP?

i just met this girl over the phone on the chat thing n she really seems to like me. she sent me a pic n i think she is cute. i sent her a pic and she said "thank you" lol n i was like "y" n she said "b/c its a good pic." n she seemed excited to give me her number cuz she asked me if i was going to ask for it or not. also she has asked if i like talking to her like twice. we have talked the last two days briefly but she called me after i had called her earlier and told me tht she would later today as well. she didnt but im not really tripping on tht. my real concern is how to get her quick but not seem desperate. im ok with my single life right now but wouldnt mind if the right person came n i think she might be it so i want to figure out how to play this upfront lol. so wht should i do as far as calling her n othr things. also she is 18 and im 22 so if tht makes a diff. then let me know. if possible give examples of how u played a similar experience before.