@Foong0 I think one of the keys to getting them to respond is to respond as quickly as possible (so that they don't book somewhere else while they are waiting), and to try to make the reply personal. For instance, in a recent request to us, a retired man from France--I'll call him "Guy"--wrote and said that he, his wife "Annette" and another retired couple were potentially interested in renting our place, and he asked a few questions.
I immediately replied with something like this:
"Dear Guy,
Thank you for your interest in our villa. We would love to host you, your wife Annette and your two friends, and we think that you will really enjoy yourselves here.
In answer to your questions, first, there is indeed a swimming pool, and it is directly across from our home--about 30 metres away. It doesn't get too crowded or noisy, even in summer, and so you should find it a great place for relaxing. (There are more details about this in our listing.)
Secondly, there are plenty of great restaurants in the local area, including a few that are only walking distance away. If you tell me the kind of food that you, Annette and your friends prefer to eat, then I can send you a list of recommendations.
Guy, please let us know if you have any other questions. We are here to help.
Regards..."
Something like that. It shows that you are paying attention to their request, that you are using their names, that you remember how many people are in their party, and that you are trying to address their needs.
Mind you, there are no guarantees that they will still book. As @Solveig0 said above, people are people, and sometimes they may not reply to you even if you do write something like this. But in our opinion, it is worth the time and effort to try. (And yes, these people did book after we had sent them that message.)
Good luck.