Hi Colleen, I guess you're asking about a social form after Polish 'Dzień dobry' in this particular situation? You're right. Neither 'Jak się pani/pan ma?' nor 'Co słychać?' would sound appropriate. IMHO there is nothing in between either probably because you're asking for something which doesn't exist in Polish language. We do not have any social form that goes after 'Dzień dobry' in such a situation that would be English equivalent of 'Hi, how are you?'. We just say 'Dzień dobry' and that incorporates both 'Hi' and 'How are you?' If you don't know the person and she is an older lady and you are determined to start a conversation, you just start a conversation with a neutral topic, question, remark, reflection and the like then, if it goes down well, you can proceed to something you're interested in. What's more, 'Dzień dobry' wouldn't sound good after standing together for a while in the same line either. It would sound as if you just noticed that woman. 'Dzień dobry' is good when you first see the other person. After a while, I'd consider it odd. So, after a while of standing together I'd say: 'Przepraszam, że przeszkadzam, ale czy...' or 'Przepraszam, że spytam...' and here some more or less neutral question or remark, or just 'Przepraszam, ...' and there you go... You can even omit 'Przepraszam' if you want to start with a general remark for example of how angry, tired or bored you are being stuck in a line. So, IMHO, if you don't know the person, don't look for any other social language after 'Dzień dobry'. Just go. If you've been standing next to them for a while, omit 'Dzień dobry', just go applying general social rules.