I recently created a tool that can be used to help make feedback more efficient and effective following a playtest session for a game. Here is a link to a PDF of that tool:
When giving a score from 1 to 7 on the points listed, it is not enough to just give a number. The idea is that the playtester will give the game a score and then briefly explain why they felt the game should be given that score.
After every playtester has had their say using this tool, then a more organic discussion can ensue. Having gone through the points on this tool before starting that discussion helps make that discussion more effective as all of the important talking points can be brought up first. Thus, the conversation will have a more focused direction.