One way that I think to stop that is the user who starts a new topic waits for his answer and when he does receive the most satisfactory reply to his topic he awards the reply a merit and then locks the topic so that no further waste gets accumulated in the topic and anyone who wishes to gain knowledge can just read the topic and get only what he exactly wants.
This practice is common among the responsible forum members. Spammers will ignore this as it is the simple way for them to increase the post counts and activities without taking any efforts. You can just report these useless post to the moderator; which is the only simple and quick action in our hand.