Are the comment replies done anonymously and privately?
That right there is the biggest reason for the forms - aside from the fact that I am addicted to forms, that is.
Anonymous... not so much, but private - the players only see another's comments if they are willing to share. Some are, some aren't.
Basically I ask questions like: 'What Did You Enjoy?'
'What Did You Not Enjoy?'
'Where Do You Think The Game Needs Work?'
'Did Your Character Learn/Figure Out Something, If So, What?'
'What Did You Do That You Thought Was Cool?'
'What Did Someone Else Do That You Thought Was Cool?'
(These last two are the closest to mandatory that I have.)
I have the forms, but most often the answers get e-mailed to me.
Players sharing feedback has helped me - I have had a player that was causing problems about Subplots (Spycraft 2.0), and on hearing the other players decided to give them another try. One result has been that he has started using Subplots in his own campaign.... (His was the game I most recently got to play in, for that matter - a mystery of a stolen Zamboni, and some Canadian hockey players who had been kidnapped by the Winter Court of fey.)
After realizing that the other players were really enjoying them he relaxed enough to give them a try. Previously he felt that taking a Subplot was like 'painting a big target on his chest.'
Other things that can help shape the game are Action Dice and Karma Dice - a mechanic that I stole from 7th Sea. One advantage is that they provide instant feedback from the GM, in mostly positive fashions.
Action Dice are dice, most often D6s, except in games like Spycraft that already has the mechanic, that the GM hands out for trying to do things that he thinks are cool. The player can spend one, and add it to any one roll.
So, if he got a 10 on a d20, and decided to add an action die, rolling a 3 then the die roll would be 13. You can't get a 'Natural 20' this way, but it helps.) It is important to hand them out for attempting, not succeeding - that way they can be spent on whatever cool thing the PC is attempting.
This means that the players learn what the GM thinks is cool, and is more likely to act accordingly. I aim at handing out about six a session - I want the PCs to act like heroes.
Karma Dice are a bit different - a small bowl of Good Karma dice in the middle of the table that the players can use - one die at a time per player, to boost someone
else's roll, adding a description of what gave the bonus (or penalty - I allow them to be used to penalize an NPC's die roll as well.)
A Bad Karma die is a black token that the GM gives to a problem player, one who is disruptive, argumentative, or just plain rude to everybody. At any time the GM can take back the token and tell the player 'You fail' - no matter what the die roll that he might have gotten. (Nothing like taking away that Natural 20 to teach a lesson.)
In theory the Bad Karma die can be taken from whatever PC earned it, then used on any other PC, but I eventually just went with it happening to the idjet who earned it. For what it is worth, I have only twice given Bad Karma dice, and this is over a goodly number of years. While I warned the players that the die could be used against anybody I only ever used it on the two idjets who earned them.
Time for bed, my typing skills are going bye bye.... Coherence evaporating.... Spelling dimbinished...fthsn.....
The Auld Grump