I’m open to all sorts of publishers, though in the Third Edition d20 world, I’m most comfortable as a DM if the third-party published material came from 1) Paizo, 2) Malhavoc Press; 3) Green Ronin; 4) Sword and Sorcery in that order.

In past editions, players would come up with the own stuff more. These days, they are more likely to find it in a supplement and offer it up.

The group that I’m playing in uses a heavily (and I do really mean heavily) modified version of the original AD&D, with some of the changes having come from Dragon Magazine, or TSR (anybody else remember them?) supplements. There really isn’t anybody publishing additions to the system anymore. The closest thing to that that we have to deal with is when people say “hey, this game here has a really interesting system for this… perhaps we could steal parts of it and try to adapt it to our system” (read: hey, can you make this fit our system for me?)

We’ve been making changes and additions to the game over time, and it’s always been completely understood that the DM is the one who makes the absolute calls as to whether things get changed, or whether they get pulled out of the game if they’re not working the way they’re supposed to. It’s worked out quite well for us to not really view any of the rules as being written in stone, since the “core rules” of any system won’t necessarily suit every group of players perfectly, and supplements don’t always hit the mark, either. Sometimes a generous application of house rules can be just what you need to make something enjoyable for the people around your particular table.

I definitely agree that it’s a lot easier to hold off on giving something to somebody, rather than being put into the situation of having to take back something that you’ve given them.

As far as supplements go, I’m lucky in that I know more about all the official and unofficial rules and options are, since I use a system that isn’t sold in most stores. I don’t like sounding like that “Cool kid with the taste in music too good for you.” I’m just one of the weirdos that actually likes Iron Crown Enterprises (I’m in love with HARP).

1) Players may present material to me to be accepted into the game.
2) If the material is easy to review (like a 2 page section) I’ll give it a read and think about it. If the material is much more time consuming to review (like a 400 page book) I suggest to the player that they run a game with that material.
3) If I approve of the material it goes into the game with a caveat that if the material make the game less fun for the group as a whole it will be revoked after a few sessions where the material is used. I try to introduce the material into the story under a premise that makes it “temporary” in nature. This can be tricky, but it allows the material to be revoked without retconning the game.

Now as I said, the material is revoked only if it makes the game less fun for the group as a whole. The players might love some new material that drives me nuts. Too bad. The group is enjoying it, and I have to adjust. Likewise the player using the material and I might not have any issue with it, but the rest of the group has less fun because of the material it should be revoked.

I’ve only had to revoke something twice. Both times the players involved understood why, and they found new materials that were a better fit. Having this process in place makes it easier to deal with those moments though, and it keeps the players from suggesting material that might upset the game’s balance.

One last note, since I skipped D&D 3.x I’m talking about different game systems here. I really didn’t have to deal with the 3rd party explosion of materials for that system.

While I currently enjoy playing a 3.5e gaming with everything available, I’m not rushing out to buy the 4e supplements. I’d like to play a few more times– or, better, one solid campaign– using the core rules before we start drawing in all of the splat books. I know, Martial Power and Adventurer’s Vault sing seductively… but I’ll see if the core is enough for now.

For D&D, there’s been an onslaught of 3rd party products. A lot of it is just plain bad, but once in a while there’s a spell, a feat, or a monster that is well-written and just too cool to exclude because it wasn’t inspired by a Hasbro paycheck.

At the same time, there’s official stuff, even in the core rules, that shouldn’t be allowd. The 3.0 ranger, for instance, with a class feature based on BAB, so that a one-level dip before multiclassing into something better meant you got all of the sweet ranger abilities. It was core, but who cares? It was bad design and any GM who rejected it would have been entirely fair in doing so.

Of course, it’s not bad to say something like, “By default, all core materials are allowed, and all secondary materials are excluded until review.” You assume the core rules are basically good enough for the game (or why are you using this system?) but if an option is revealed to be problematic, it’ll get changed or removed. For supplements, nothing is in automatically, but, as GM, you’ll give materials the player would like to use a read and make an informed decision. That doesn’t mean, “Hey, can you read this 300 page book and tell me it’s cool?” but rather, “Here’s a feat and a spell that I think fit my character well and I’d like to use them; let me know what you think.”

That’s great and all, but -yes-, it is hard to eliminate them once they’ve made their way onto a character sheet, and even harder once they’ve been used. People get attached to their characters. It’s generates fewer hard feeling to say “No, you can’t be an elven sworddancermagearcher” than it does to start trying to line item stuff off someone’s character sheet once you’ve opened the pandora’s box.

An ounce of prevention is worth the proverbial pound of line item vetoes here. At the very least, you need to vet supplements with a thorough reading before you allow them, and that’s time a lot of people don’t have.

Players want options and generally there are rules in place to keep track of that. If they feel things are unbalanced between them, they can police themselves. I don’t worry about it. If something is unbalanced, it usually becomes apparent quickly and is easily dealt with. After all, you, as the DM, are holding all the big guns.

I’ve always regarded DMs that state ‘core rules only’ as a bit stifling and paranoid, with just a touch of laziness. All you have to do is make sure statistical norms are followed. If a character’s say..difficulty to be hit, amount of damage dealt, or some other fishy thing goes up, you know something is wrong. Just a matter of glancing over character sheets from time to time.

There are certainly things that are broken, but is it really that hard to eliminate them once they’ve cropped up? You as a DM should be able to line item veto anything, core rules included.

I agree with the variant thing. I think that’s an excellent rule of thumb.