Most Helpful Guy
Unless i already had a fun conversation with that person before i don't. No point in keeping a conversation going with someone who doesn't know to participate. If they ran out of things to say and i want it to continue ill bring up a new subject to reignite the conversation so they don't have to struggle or have it be awkward.
Most Helpful Girl
It really depends on what context. However, if you are wondering about how to progress the conversation or if you should I'd say, just bring up something you did today or saw or ask a question.