How to keep conversation going well?

How do I keep a conversation going with this girl?

• At the gym I go to there is this receptionist girl shes a few years older than me she is in her 20's and I am 18.I am a regular at the gym I go at the same time everyday so she recognizes my face now. I always but a protein shake from her before I leave and have a brief conversation like I ask her how was work or she tells me shes sleepy cause she has to work late or she tells me shes bored or she asks how my workout was Its always a brief conversation and its usually while shes making the smoothie and after that we just stop talking and she watches the tv and I just sit their quietly drinking my shake How can I have a more lengthy conversation with her what should I say she seems like a very nice friendly person that's why I wanna talk to her

• Answer:

  Tell her one day that you have to go without getting a shake. This way you can make her miss the conversation that she enjoys (or else she wouldn't keep talking to you). Ask her when she gets off work and ask her to go get some coffee or something. Keep it causal. Dont make it seem like a date.