I've seen it done both ways.
1/ A person makes a motion and someone else seconds it. the Chair calls for discussion. People speak in turn, some supporting, some opposing, some asking questions and seeking clarification, some suggesting things that might make it a better motion. Sometimes there is a friendly amendment that both the original person and the seconder agree upon. After a bit the Chair asks if there is any further discussion, then calls for the vote, and the motion is either passed or defeated.
2/ Somebody asks a question or makes a statement and a discussion comes up. People exchange ideas, ask more questions, argue, make alternate suggestions, mention something quite unrelated, get back on topic, etc. Finally the Chair calls for a motion. Somebody makes the motion, and it is seconded. Then the Chair immediately calls for a vote without any further discussion on the motion or how it is worded.
I think I prefer the first method. Get a motion on the floor, have if discussed, either pass or defeat it. The second gives no room to discuss the actual motion. Discussion before it is made might not have direction and might cover a lot of things not directly related to the motion.
Or is there room for compromise between the two methods.