I got some nice feedback and commentary on my First Time Always Works post.
I do have some clarifications about it.
It has to be possible or probable.
In other words, this ruling approach wouldn't say "Anything you think of works the first time." It's a "tie always goes to the players" or "edge cases are always in your favor" or "Maybe means yes" rule. It's not a "Yes to everything the first time" rule.
It can't change the facts on the ground.
Again, it's edge cases. Perhaps this time you sharpen a silver coin and tie it to a stick and it works as an arrow against the lycanthrope. But you can't just throw a coin at the lycanthrope and except it'll die, or say, "I've heard they are also vulnerable to gold pieces" and use gold instead. You're getting the favorable bounce, not getting to change the world.
Impulse Buys works, if you have players that use them.
Mine wouldn't spend a character point on a fleeting gain, no matter how critical that fleeting gain is. And I haven't gotten into handing out impulse point pools. So I didn't even go there. But yes, if you're using Impulse Buys, the GM is within this rule by asking you to pay to invoke it.
Significant difference matters.
"We did the jumping off the cliff and half-falling with Levitate and it worked that one time, so let's do it this time with Flight. Or "Last time we did that, it was everyone in the party. This time it's half of the party, so that's not the same thing." Pretty much as soon as there is a last time, that sets the outside limit of precedence.
The GM can still say no.
This is critical. Again, it's edge cases. It's, "I'm okay with that happening in the world." The GM can still say no. It's the basis for a ruling, not a contractual agreement to say yes. It's more player-limiting then player-enabling, in a way, but provides an understanding of what those limits actually are.