Old School DM, New-School Players?

Its a common complaint on the interwebs, usually something along the lines of "I'd love to run (insert OSR game of choice), but all anyone around here wants to play is (insert D&D 3.5, 4E, or Pathfinder)". A lot of DMs will eventually face the choice of running a contemperary edition or running nothing at all. If you don't wish to take the latter option, here are some quick and easy House Rules that can make those new systems feel a little more "old-school":

Attacks of Opportunity
Get rid of these. One of the biggest "old-school" complaints about newer editions is how combat becomes too focused on the grid-board, and less in the imagination. Eliminating attacks of opportunity can go a long way toward getting rid of the mentality of manuevering pieces on the grid for the best advantage. Make sure your players know about this houserule at character generation time, because a lot of Feats and Skills can relate to AoO's. For PCs with special abilities tied to AoO's, like the Rogue's Sneak Attack, simply have the player describe how he is manuevering, and be more liberal than restrictive in allowing him to use these class abilities.

Level Cap
The biggest differences between older and newer editions tend to reveal themselves in high-level play. Don't be afraid to set a level cap on your game. I recommend 10th level as a good benchmark; numbers don't really get too crazy until then. You can also take a look at alternate xp progression tables. Doubling the xp's required for each level is a good way to extend low-level play, or you can just run them as-is and enjoy some good old-school endgame scenarious built around establishing strongholds. Again, be sure to let players know this going into the campaign, as many "new-school" players put a lot of emphasis on character "builds", which involves long-term planning of class, skill, and feat allotment.

Critical Hit Confirmation Check
Do away with this. It just adds another roll to what may be an already "swingy" combat. I highly doubt the players will mind the increased chance of a critical hit, and this can help combats be a bit faster. This houserule doesn't impact alot of feats and skills either, so its easy to implement.

Class/Race Selection
Don't be afraid to limit the classes or races available in your campaign. If you feel strongly that Half-dragon Favored-soul/Templars will be disruptive to the old-school feel of your campaign setting, try setting some boundries, perhaps making only the traditional races and classes available at first.

Skills
Player Actions should trump Skill Checks. For an old-school DM, gathering information about a lost city, dark cult, or infamous Megadungeon can turn into a whole night of fantastic role-play, unexpected situations, and cooperative world-building. Unfortunately, in many newer edition systems, you can reduce all that into one quick Skill Check. Let players know you won't be using just that Skill Check. Make them play it out. Skill checks should only come into play if the outcome of the situation, as modified by their actions, is somehow in doubt. Or, you can use those well-laid plans to determine a modifier to that skill check roll. A well thought-out and implemented plan should never fail just because of a flubbed roll, and a nat-20 remove traps check should never trump obvious bumbling and stupidity!

Game Balance
Newer edition adventures are often very linear, and are frequently defined by a series of encounters designed to be challenging for an oppopriate level, and provide the "proper" amount of xp and treasure to keep the game "balanced". If you're using a published adventure, take a bit of time to go through and adjust a few encounters up and down in power level. Once the players have gotten out of the expectation of balance, your sessions should proceed in a decidedly more old-school fashion, as players get out of the comfort zone of knowing that every encounter is winnable and start to do a bit more scouting, exploration, and research to balance the odds themselves. This is especially easy to implement in games where a level cap has been established.

Communicate
Be up front with your players about these "old-school" modifications to your campaign, and explain why you feel the modifications are necessary. Always remember that the elements of newer editions that annoy and repulse you may be the elements that your players really enjoy, so its important to compromise where possible, and focus on the elements you all enjoy in common. At the end of the day, getting together with folks and having a great time is far more important than any sort of "edition loyalty", and most rules are easy to modify to taste.

P.S. - Old School One Shots
Always keep a copy of your preferred OSR edition of choice with you. Its not unusual that real-life roadblocks can arise and players can be absent from a session, leaving you with the choice of skipping the game altogether that week, or running a one-shot for the players that are available. This is a fantastic opportunity to demo that old-school game you keep trying to sell them on!