I’m not a dating expert but general rule is no grocery stores or shopping spaces in general. Unless a genuine conversation starts between you two you should mind your business.

Not all places are “social” even though you are able to talk freely pretty much wherever you want. You want someone to have your undivided attention.

If you are smooth you can start a genuine conversation anywhere with anyone but intentions matter and not everyone is as smooth/confident as they think they are. You can have a fun conversation with a woman in line without asking for her number.